Equipment, system and method for independently managing reverse link communication resources in a distributed communication system

Abstract

"EQUIPMENT, SYSTEM AND METHOD TO MANAGE REVERSE LINK COMMUNICATION RESOURCES INDEPENDENTLY IN A DISTRIBUTED COMMUNICATION SYSTEM". An equipment, a system and a method efficiently manage reverse link communication in a communication system having geographically distributed base stations. A base station functioning for at least one mobile station as an active non-server base station estimates an expected coupled load due to at least one mobile station based on a previous total coupled load. The base station determines total available capacity based on the difference between the total capacity of the base station and the estimated expected coupled load. The base station allocates reverse link resources to other mobile stations served by the base station so as not to exceed the total available capacity. Since the allocation of reverse link channel resources is controlled by the base station, delays due to communications with a central controller are eliminated. As a result, the adverse effects of load programming are minimized based on obsolete information from the reverse channel.

Description

"EQUIPMENT, SYSTEM AND METHOD FOR AUTONOMOUSLY MANAGING REVERSE LINK COMMUNICATION RESOURCES IN A DISTRIBUTED COMMUNICATION SYSTEM" BACKGROUND OF THE INVENTION The invention relates generally to communication systems and, more specifically, to equipment, a system and a method for managing reverse link (upilink) communications in a distributed communication system. Several wireless communication systems employ geographically distributed base stations to provide communication cells or regions where a serving base station provides communication service to mobile stations within the region corresponding to the serving base station. In certain situations, reverse link signals transmitted from each mobile station to a base station interfere with other reverse link signals transmitted from other mobile stations. Due to interference and limited resources, the capacity of each base station is limited.A base station's reverse link capacity is affected by the reverse link load due to mobile stations served by the base station, the reverse link coupled load due to mobile stations served by other base stations, and other noise sources. Reverse link load scheduling provides a mechanism to maximize the efficient use of system resources by controlling mobile station transmissions. In conventional communication systems, a centralized controller evaluates the reverse link load and reverse link coupled load, as well as other factors, to determine the appropriate load schedule. However, for most data applications, mobile stations are controlled by a single serving base station to reduce scheduling delays, even though reverse link transmissions can affect the load on other base stations. However, conventional systems are limited in several ways. For example, communications with the centralized controller result in significant delays. The information gathered by each base station is forwarded to the centralized controller. The centralized controller processes the information, determines an ideal load capacity for each base station, and sends the ideal load capacity to each of the base stations. Each base station limits the communications of the mobile stations it is serving according to the updated load capacity provided by the controller. However, channel conditions frequently change during the time required to transmit, process, and receive the ideal load capacity. Therefore, a base station may be operating at a significantly different level from the ideal level, resulting in unused resources or an overload condition.An overload condition can occur, for example, when a base station operating according to the latest optimal capacity information provided by the controller can overload another base station that is trying to operate near its maximum capacity, because system delays prevented the new channel conditions from being reflected in the information transmitted to the base stations. Overload conditions lead to data loss, message retransmissions, and other undesirable consequences. Therefore, there is a demand for equipment, a system, and a method to efficiently allocate reverse channel resources in a communication system with geographically distributed base stations. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a communication system having geographically distributed base stations according to exemplary embodiments of the invention. Figure 2 is a block diagram of a part of the communication system in which a single mobile station is in communication with base stations functioning as a serving base station and a non-serving base station. Figure 3 is a block diagram of a base station according to an exemplary embodiment of the invention. Figure 4 is a block diagram illustrating an exemplary relationship between mobile stations and base stations according to exemplary embodiments of the invention. Figure 5 is a table illustrating the exemplary relationship between mobile stations and base stations according to exemplary embodiments of the invention.Figure 6 is a graphical illustration of an exemplary distribution of reverse link loads and reverse link coupled loads experienced at a base station according to exemplary embodiments of the invention. Figure 7 is a block diagram of a part of the communication system according to the first exemplary embodiment of the invention. Figure 8 is a flowchart of a method for determining an expected coupled load performed at a serving base station according to the first exemplary embodiment of the invention. Figure 9 is a flowchart of a method for determining an available capacity at a non-serving base station according to the first exemplary embodiment of the invention. Figure 10 is a flowchart of reverse link channel resource management in the communication system according to the first exemplary embodiment of the invention.Figure 11 is a block diagram of a part of the communication system according to a second exemplary embodiment of the invention. Figure 12 is a flowchart of a method for managing reverse link channels implemented in a base station functioning as a server base station according to the second exemplary embodiment of the invention. Figure 13 is a flowchart of a method for managing reverse link channel resources in a base station functioning as a non-server base station according to the second exemplary embodiment of the invention. Figure 14 is a flowchart of a method for allocating reverse link channel resources in a communication system having geographically distributed base stations according to the second exemplary embodiment of the invention.Figure 15 is a block diagram of a portion of a communication system providing communication services to mobile stations with geographically distributed base stations according to the third exemplary embodiment of the invention. Figure 16 is a flowchart of a method, implemented at a base station, for managing reverse link resources in a communication system having geographically distributed base stations according to the third exemplary embodiment of the invention. DETAILED DESCRIPTION OF PREFERRED MODALITIES A device, a system, and a method manage reverse link communication in a distributed base station communication system. In the exemplary embodiments described herein, reverse link communication is managed in a distributed manner by base stations within a communication system. The delays associated with conventional techniques for managing reverse link channels are avoided, since reverse link management does not depend on communications with a central controller. In a first exemplary embodiment, a non-server base station determines a load-coupled indicator based on load-coupled parameters detected at the non-server base station due to a mobile station identifying another base station as the server base station.Load-coupled parameters are parameters that provide an indication of the load coupled experienced at the non-serving base station and may include parameters such as a normalized and average received signal-to-noise ratio (SNR) and a mobile station speed. A load-coupled indicator based on the load-coupled parameters is sent to the serving base station. The serving base station calculates an expected load coupled at the non-serving base station based on the load-coupled indicator and a mobile station transmission parameter such as a scheduled transmission data rate. The expected load coupled is sent to the non-serving base station, where the non-serving base station calculates the available capacity considering the expected load coupled. Mobile stations served by the non-serving base station are scheduled in terms of load according to the calculated available capacity. In a second exemplary embodiment, a non-serving base station calculates the maximum tolerable coupled load due to mobile stations that are programmed by some other serving base station. The non-serving base station determines a coupled load indicator based on coupled load parameters (such as a normalized and averaged received signal-to-noise ratio (SNR)) at the non-serving base station due to each mobile station that has identified some other base station as the serving base station. In the second exemplary embodiment, the maximum tolerable coupled load associated with the non-serving base station is forwarded to the serving base station in each programming period, and the mobile station-measured coupled load indicators are forwarded to the serving base station at a relatively lower frequency.Since the serving base station being considered may also be a non-serving base station for some other mobile stations, the serving base station also determines a maximum tolerable coupled load from the mobile stations that are served by other base stations. The base station performs load scheduling according to the maximum tolerable coupled load reserved for mobile stations that are not being scheduled by the base station, while also respecting the restrictions imposed by the maximum tolerable coupled load received from other base stations. In a third exemplary embodiment of the invention, a serving base station programs the reverse link transmissions of the mobile station according to an estimated expected coupled load due to reverse link transmissions from mobile stations served by other base stations. Each base station estimates the expected coupled load due to mobile stations served by other base stations. Based on the estimated coupled load and the base station's capacity, the base station's load programs the mobile stations served by the base station. In the third exemplary embodiment, therefore, the base stations do not receive explicit or direct coupled load information from other base stations. Thus, the third exemplary embodiment is particularly useful when the return transport channel does not support the communication of coupled load information between base stations.Although several techniques can be used to calculate the estimated coupled load, the estimates are based on previous reverse link transmissions from mobile stations in the exemplary third mode. Each base station measures the coupled load from mobile stations not scheduled by the base station based on actual transmission rates and measured SNR. Previous coupled load measurements are fed into a statistical function that estimates the expected coupled load during the next scheduled transmission. The statistical function is based on correlation which can, under certain circumstances, be adaptively modified. The "blind" determination of the expected coupled load, within a certain margin, determines the capacity available to the base station to schedule the mobile stations served by the base station.Figure 1 is a block diagram of a communication system 100 providing communication services to mobile stations 110, 112, 114 using geographically distributed base stations 102, 104, 106, 108, according to exemplary embodiments of the invention. Figure 2 is a part 200 of the communication system 100 in which a single mobile station 202 is in communication with the base stations (102 to 108) functioning as a server base station 204 and a non-server base station 206 for mobile station 202. At any particular time, a base station (102 to 108) may function as a server base station 204 or a non-server base station 206 for a particular mobile station (110 to 114) or may not perform any function directly for mobile station (110 to 114). For clarity, four base stations 102, 104, 106, 108, and three mobile stations 110, 112, 114 are shown in Figure 1.The communication system may include any number of base stations (102 to 108) and mobile stations (110 to 114), as well as other communication devices. In the exemplary embodiments presented, communication system 100 is a cellular communication system using code division multiple access (CDMA) communication techniques to provide voice and data services. Those skilled in the art will readily recognize the various other types of communication systems 100 suitable for use with the invention, by applying the teachings described herein in accordance with known techniques. Each base station 102, 104, 106, 108 provides wireless communication service to mobile stations (110, 112, 114) in a coverage area 116, 118, 120, 122, or cell. Coverage areas 116 to 120 overlap in such a way that a mobile station 110 to 114 can be communicating with more than one base station 102 to 108 at any given time. If a mobile station 110 to 114 is within the coverage area of ​​a base station 102 to 108, the mobile station 110 to 114 will identify the base station 102 to 108 as an active base station. However, as will be discussed in more detail later, only one base station (102 to 108) functions as a server base station 204 for a particular mobile station 202 (110 to 104) for data communication. A server base station 204 is the base station responsible for scheduling the next transmissions of a mobile station 202.Figure 1 includes exemplary shapes surrounding each base station 102 to 108, representing service regions 116, 118, 120, 122, where base station 102 to 108 is most likely to function as the serving base station 204 for mobile stations 202 (110 to 114) within the serving region 116 to 122. Each mobile station 110 to 114 maintains a set of active base stations in memory, where members of the set communicate via communication links that meet the necessary criteria. An example of a suitable method for selecting active base stations (102 to 108) for a mobile station 110 to 114, 202 includes identifying a base station 102 to 108 as an active base station (102 to 108) 204, 206, when a signal transmitted from base station 102 to 108 is received at mobile station 110 to 114 at a suitable level.In exemplary embodiments, active base stations (102 to 108) 204, 206 are selected based on the signal strengths received from pilot signals transmitted from base stations 102 to 108, 204, 206. In some circumstances, other techniques may be used to select active base stations (102 to 108) 204, 206. Active base stations (102 to 108) 204, 206 provide communication service to a mobile station 110 to 114, 202, where the quality of service and data rate may vary between base stations 102 to 108 due to various reasons. In the exemplary embodiment, one of the active base stations (102 to 108) is selected as a server base station 204 for communication of data other than voice information. Any of several techniques and criteria may be used to select the server base station 204. The server base station 204 may be selected based on characteristics of the forward communication link 210 (from base station 102 to 108 (204) to mobile station 110 to 114 (202)), the reverse communication link 212 (from mobile station 110 to 114 (202) to base station 102 to 108 (204)), or the forward and reverse communication links 212, 210. The quality of the forward and reverse link channels 210, 212, for example, may be determined by measuring the carrier / interference ratio of the channel. In the exemplary mode, the information contained in a reverse link channel quality indicator is used to identify the server base station 204, which is identified by the R-CQICH channel.The serving base station 204 responds to communications from the mobile stations 202 it is serving by performing various tasks such as allocating data transmission rates through scheduling grants and maintaining the received SNR of the reverse link pilot above a limit by sending power control commands. Additionally, a serving base station 204 decodes transmissions from mobile station 202 and sends acknowledgments (ACKs) in the case of hybrid ARQ, while a non-serving base station can also decode a transmission and send an ACK in the case of a soft handoff.The shapes included representing the coverage regions in Figure 1 define exemplary geographic service regions 116 to 122, where mobile stations 110 to 114 within region 116 to 122 will likely have adequate communication with the corresponding base station 102 to 108 to identify base station 102 to 108 specifically as the serving base station 204. However, other base stations (102 to 108) may act as active base stations (102 to 108) 206 for a mobile station 110 to 114, 202. As illustrated in Figure 1, therefore, a first mobile station 110 is within a first service region 116 provided by the first base station 102, a second mobile station 112 is within a second service region 118 provided by the second base station 104, a third mobile station 114 is within a third service region 129 provided by the third base station 106 and the fourth base station 108 provides a fourth service region 122.Figure 3 is a block diagram of a 300 base station according to an exemplary embodiment of the invention. The exemplary 300 base station is suitable for use as any of the 102 to 108, 204, and 206 base stations described with reference to Figure 1 and Figure 2. The 300 base station may include any combination of hardware, software, and firmware that performs the functions of the 102 to 108 base stations. The functions and operations of the blocks described in Figure 3 may be implemented in any number of devices, circuits, or software. Two or more of the functional blocks may be integrated into a single device, and the functions described as being performed in any single device or block may be implemented in multiple devices. For example, some reception processes may be performed by the 304 processor.The base station includes a radio transceiver 302 configured to communicate with mobile stations 110 to 114 according to the protocols of the particular communication system 100. Radio frequency signals are exchanged via antenna 308, which may include sectors in some circumstances. Radio transceiver 302 modulates, amplifies, and transmits signals through forward link channels 212 and receives and demodulates reverse link signals transmitted by mobile stations 110 to 114 through reverse link channels 210. Processor 304 is any combination of processor, microprocessor, computer, microcomputer, or processor suitable for performing the control and calculation functions of the base station 300 described herein, as well as for facilitating the general functionality of the base station 300. The software code running on processor 304 executes the steps of methods for measuring and processing signals and for performing the reverse link management functions of the exemplary modes.A return transport channel interface 306 provides an interface to the return transport channel 208 of the communication system 100. The return transport channel interface 306 includes hardware and software for exchanging signals through the return transport channel 208. The processor 304 transmits and receives information to and from controllers and other base stations 102 to 108 through the return transport channel interface 306. Figure 4 is a block diagram and Figure 5 is a table 500 illustrating an exemplary relationship between mobile stations 110 to 114 and base stations 102 to 108 according to exemplary embodiments of the invention.The solid lines connecting base stations 102 to 108 to mobile stations 110 to 114 in Figure 4 represent a connection between mobile stations 202 (one of 110 to 114) and their corresponding server base stations 204 (one of 102 to 108), and the dashed lines represent connections between mobile stations 202 (one of 110 to 114) and their active non-server base stations 206 (one of 102 to 108). As described herein, an active non-serving base station 206 (102 to 108) is a base station 300 identified in the set of active base stations of a mobile station 202 that is not a serving base station 204. In the exemplary embodiment illustrated in Figure 4 and Figure 5, each mobile station 110 to 114 maintains a set of active base stations that includes the serving base station 204 corresponding to service region 116 to 122 containing mobile station 110 to 114 and all other base stations (102 to 108) that are active non-serving base stations (102 to 108).Therefore, for the exemplary case, all base stations 102 to 108 are maintained as active base stations by each of the mobile stations 110 to 114. A mobile station at a significant distance from a base station cannot maintain the base station in the set of active base stations, and the base station will not be identified as a non-serving base station for the mobile station even if the base station may receive reverse link interference from the mobile station. Only those mobile stations whose signal strength is sufficient and whose transmissions are processed are considered by a base station. Briefly referring to a single mobile station 110, the first base station 102 is the serving base station 204 for the first mobile station 110, 202, and the second base station 104, the third base station 106, and the fourth base station 108 are non-serving base stations 206 for the first mobile station 110, 202.The reverse link transmissions from each of the mobile stations 110 to 114 are therefore received at each of the base stations 102 to 108, even though only one of the base stations 102 to 108 is acting as the server base station 204 and the other base stations are acting as non-server (active) base stations 206 for any particular mobile station 110 to 114 in this example. As a result, the reverse link loads and reverse link coupled loads experienced at a base station 102 are due to the reverse link loads of the mobile station 110 served by the base station 102 and the coupled loads resulting from the transmission of other mobile stations 112, 114. Figure 6 is an illustration of a pie chart or load sector 600 of an exemplary distribution of reverse link loads and reverse link coupled loads experienced at a base station 102 to 108 according to exemplary embodiments of the invention.The various sections 602 to 608 of the load pie chart represent the combined reverse link load resulting from mobile stations 110 to 114 that can be measured or simulated for an exemplary situation. At any base station 102 to 108, the total combined reverse link load may result from transmissions originating from mobile stations 110 to 114, where each portion (602 to 608) of the total reverse link load is due to mobile stations (110 to 114) in a particular category. The load portions (602 to 608) may include a non-serving coupled load portion 602, a non-single serving load portion 604, a single serving portion 606, and an unaccounted or unconsidered coupled load portion 608.The non-server coupled load portion 602 includes the reverse link coupled load due to all mobile stations (110 to 114) that include base station (102 to 108) in their active base station sets, but are being served by base stations (102 to 108) other than base station (102 to 108). Mobile stations 110 to 114 contributing to the non-server coupled load portion 602, therefore, have not identified base station (102 to 108) as the server base station 204. The non-unique server load portion 604 includes the combined reverse link load of all mobile stations 110 to 114 that are being served by base station (102 to 108), but include other base stations (102 to 108) in their active base station lists.Mobile stations 110 to 114 contribute to the non-unique server load portion 604, therefore identifying base station (102 to 108) as the server base station, but also identifying other base stations (102 to 108) as active non-server base stations. The unique server load portion 606 includes the combined reverse link load of all mobile stations served by base station (102 to 108), where base station (102, 108) is the only base station in the set of active base stations of any of the mobile stations 110 to 114. The unconsidered load portion 608 includes all other reverse link signals and noise that contribute to the total reverse link load, which were not included in any of the other load portions 602, 604, 606.An example of a source that can contribute to the unconsidered load portion 608 includes reverse link transmissions from mobile stations that do not include the base station in their active pool, but are close enough to the base station to contribute to the total coupled load. Such mobile stations are too far away to have an adequate communication link with the base station to include the base station in the pool of active base stations, but the sum total of their insignificant contributions is large enough to occupy a portion of the reverse link capacity. The relative size of the load portions 602 to 608 will vary over time in most cases due to constantly changing channel conditions.Fluctuating channel conditions can be due to several factors, such as the movement of mobile stations 110 to 114, the movement of obstacles, or the need to offload mobile stations 110 to 114 and transfer mobile stations between base stations due to the severely non-uniform distribution of mobile stations 110 to 114. When the combined load of all portions 602 to 608 exceeds the capacity of base station 102 to 108, the quality of service (QoS) for mobile stations suffers, the system becomes slightly unstable, and cell coverage decreases, leading to dropped calls. When the load is less than the capacity of base station 102 to 108, inefficient resource utilization can occur if data rates are not adjusted according to the requests of mobile stations 110 to 114.According to exemplary embodiments, reverse link communications are managed by base stations 102 to 108 to efficiently allocate reverse link resources to (load scheduling) mobile stations 110 to 114. Reverse link resources include, for example, data rates and power levels that contribute to a load for base station 102 to 108. Figure 7 is a block diagram of a part 700 of a communication system 100 providing communication services to mobile stations 110 to 114 with geographically distributed base stations 102 to 108 according to the first exemplary embodiment of the invention. In most cases, the communication system 100 includes several base stations 704, 706, which are strategically positioned to provide wireless communication services to numerous mobile stations 702.Depending on the quality of the communication channels between a mobile 702 station and the base station (704, 706), the mobile 702 station may be communicating with more than one base station (704, 706) at any given time. As discussed above, each mobile 702 station maintains a set of active base stations, where the communication links between the mobile 702 station and the active base stations 704, 706 are adequate for communication. Of the active base stations, one base station acts as the 704 server base station, while the other base stations in the active set are non-server 706 base stations. Such situations typically occur during a soft handoff where a single base station performs the functions of a 704 server base station and one or more other base stations are non-server 706 base stations.When conditions permit, the role of the serving base station 704 is transferred to a base station that was previously functioning as an active non-serving base station 706 (i.e., a handoff occurs). For clarity, Figure 7 includes blocks representing a mobile station 702 and two active base stations 704, 706, including a serving base station 704 and a non-serving base station 706. Those skilled in the art will note, based on the present teachings and known techniques, that a base station 300 can function as a serving base station 704 for multiple mobile stations 702 and that any mobile station 702 can maintain any number of active base stations 704, 706. The teachings discussed here, therefore, can be extended to any number of mobile stations 702, serving base stations 704, and non-serving base stations 706. As will be described in greater detail later, the other base stations 300 may not have a communication link with the mobile station 702 of sufficient quality to become an active base station, but they can contribute to the load experienced by any of the active base stations 704, 706.The serving base station 704 can be the first base station 102, the second base station 104, or the third base station 106 described above with reference to Figures 1 to 4. The serving base station 704 can also function as a non-serving base station 706 for another mobile station (not shown in Figure 7), and the non-serving base station 706 can function as a serving base station 704 for other mobile stations (not shown in Figure 7). Thus, a base station 102 to 108 can simultaneously function as a serving base station 704 for some mobile stations 702 and as a non-serving base station for other mobile stations. The functions described here for each of the base stations 704, 706, are therefore simultaneously performed by the other base station in most circumstances. In the first exemplary embodiment, a base station 300 operating as the non-serving base station 706 determines an expected available capacity based on an expected coupled load 712 received from another base station 300 operating as the serving base station 704, wherein the expected coupled load 712 indicates an expected coupled load on the non-serving base station 706 resulting from reverse link transmissions 210 from a mobile station 702 being served by the serving base station 704. The serving base station 704 determines the expected coupled load 712 using the coupled load indicator 710 received from the non-serving base station 706 and the parameters associated with the next scheduled data transmission rate.If there are multiple mobile stations 702 served by the serving base station 704, and which include the non-serving base station 706 as a non-serving base station, the expected coupled load 712 can be the sum of the expected coupled loads determined for each of the mobile stations based on the expected coupled load 712 and the programmed transmission data rates. The non-serving base station 706 receives and processes the reverse link transmissions 210 from mobile station 702 to determine one or more coupled load parameters, such as a normalized and average received signal-to-noise ratio (SNR). An example of another coupled load parameter is the speed of mobile station 702. Based on the coupled load parameters, the non-serving base station 706 calculates the coupled load indicator 710. The coupled load indicator 710 is forwarded to the serving base station 704.Serving base station 704 determines an expected coupled load on non-serving base station 706 using the coupled load indicator 710 and a transmission parameter from mobile station 702. The expected coupled load is the reverse link coupled load that will result on non-serving base station 706 due to an anticipated future reverse link transmission from mobile station 702. Serving base station 704 forwards a value representing the expected coupled load 712 to non-serving base station 706. Non-serving base station 706 calculates the expected available capacity on non-serving base station 706. Using the expected available capacity, non-serving base station 706 manages reverse link transmissions from other mobile stations (not shown) that are served by non-serving base station 706 through appropriate load scheduling of the mobile stations it is serving.When there is more than one mobile station 702, the non-serving base station 706 measures and computes a load-coupled indicator 710 for each mobile station 702 that keeps the non-serving base station 706 within the active set. A load-coupled indicator 710 is forwarded to each serving base station 704 associated with the mobile stations 702 that identify the non-serving base station 706 as an active base station. In the first exemplary embodiment, the 710 charge-coupled indicator is a chip energy / noise plus interference (Ecp / Nt) ratio, where Ecp represents the pilot signal chip energy. If the reverse link pilot is power-controlled, an expected average (Ecp / Nt) is computed from the average chips (Ecp / Nt) over a particular duration. The 710 charge-coupled indicator can be the expected average (Ecp / Nt), or any function of the expected average (Ecp / Nt). Although other methods may be used in some circumstances to forward the load-coupled indicator 710 to the server base station 704, the load-coupled indicator 710 is transmitted via the return transport channel 208 in the first exemplary embodiment. Therefore, appropriate messages and addressing are used to pass the load-coupled indicator 710 through the return transport channel 208. The return transport channel interface 306 performs any transformations or processing required to exchange the load-coupled indicators via the return transport channel. In some circumstances, the load-coupled indicator 710 may be transmitted via a direct communication link between the non-server base station 706 and the server base station 704.For example, a point-to-point radio frequency or microwave system link can be used for transmission of the 710 charge-coupled indicator in some situations. Furthermore, in some circumstances, the 710 charge-coupled indicator can be conducted via the 702 mobile station. In the first exemplary embodiment, the serving base station 704 identifies the mobile stations 702 expected to transmit during the next transmission cycle and generates the expected coupled load 712 based on the coupled load indicators 710 (e.g., Ecp / Nt) received from the non-serving base station 706 and the transmission data rate that has been authorized (scheduled) for mobile station 702 to use during the next transmission. The transmission parameter, therefore, includes at least the expected data rate of mobile station 702 in the first exemplary embodiment. In addition, other transmission parameters may be used to calculate the expected coupled load at the non-serving base station 706, such as secondary pilot transmissions or the traffic / pilot ratio of control channels.In cases where autonomous transmission occurs through control and voice channels, the expected coupled load 712 can consider the expected average coupled load contributed by such channels. In the first exemplary embodiment, the expected coupled load 712 is some function of the expected Ecp / Nt that will be experienced by the non-serving base station 706 in the predicted future transmission of mobile station 702 and other transmission parameters, including the programmed transmission data rate. The serving base station 704 generates the expected coupled load 712 based on the coupled load indicator 710 and forwards the expected coupled load 712 to the non-serving base station 706. The expected coupled load 712, therefore, is based on the Ecp / Nt measured at the non-serving base station 704, the reverse link transmission power on the control and voice channels, and the data rate on the traffic channel of mobile station 702 in the first exemplary embodiment.However, the expected coupled load 712 may represent other values ​​in some circumstances. For example, the expected coupled load 712 may represent an expected change in the coupled load that will be experienced at the non-serving base station compared to a previous transmission. When the serving base station 704 is serving more than one mobile station 702 that includes at least one other non-serving base station 706 in the set of active base stations, the serving base station 704 generates an expected coupled load 712 for each non-serving base station 706 that forwarded a coupled load indicator 710 to the serving base station 704. Therefore, any particular base station 300 operating as a non-serving base station 706 can receive an expected coupled load 712 from any number of base stations 300 operating as serving base stations 704. In the first exemplary embodiment, the expected coupled load 712 is transmitted through the return transport channel 208 to the non-serving base station 704. The return transport channel interface 306 performs the processing and formatting required for transmitting the expected coupled load 712 through the return transport channel 208 to the base station 300 acting as the non-serving base station 704. In some situations, other techniques may be used to forward the expected coupled load 712. After a base station 300 has received the expected coupled load 712 from all appropriate serving base stations 704 and mobile stations 702 contributing to the non-serving coupled load portion 602 of the total load, the non-serving base station 706 (300) determines the available capacity. The total of all expected coupled loads 712 constitutes the expected non-serving coupled load portion of the total load at base station 300. The available capacity is the difference between the total capacity of the non-serving base station 706 (300) and the total of the expected non-serving coupled load portion (402) and the unaccounted load portion 408.After taking into account the loads due to voice or fundamental reverse channel traffic, the available capacity (CAV) in a 300 base station can therefore be expressed as: CAV = CTOT - (LoadEx + LoadUA) where CTOT is the total capacity of the cell after taking into account the loads due to voice and fundamental reverse channel traffic; LoadEx is the expected non-server coupled load due to mobile stations that are served by other base stations and for which the base station is included in the set of active base stations; and LoadUA is the load due to other sources. Using the available capacity, base station 300, functioning as a non-serving base station 706 for mobile station 702, allocates reverse link resources (load schedules) to the mobile stations (not shown) that it is serving. In the exemplary embodiment, the non-serving base station 706 schedules the load of mobile stations that do not have any other base stations in their active base station after allocating resources to the mobile stations while maintaining other active base stations. Figure 8 is a flowchart of a method for determining an expected coupled load performed on a base station 300 functioning as a serving base station 704 for at least one mobile station 702 according to the first exemplary embodiment of the invention. In some circumstances, the method described in Figure 8 is performed on base station 300 which is also functioning as a non-serving base station 706.The method described with reference to Figure 8 is performed when at least one non-serving base station 706 is maintained in the active base station set of at least one mobile station 702 that is being served by the serving base station 704. The techniques described herein can be applied to any number of base stations 300 and mobile stations 110 to 114. In exemplary embodiments, the methods are performed at least partially with software code running on processor 304 within one or more base stations 300. Those skilled in the art will readily recognize the various techniques that can be used to implement the methods described based on the present teachings according to known techniques. In step 802, a coupled load indicator 710 is received from a base station 300 operating as a non-serving base station 706 for at least one mobile station 702. The coupled load indicator 710 indicates the coupled load measured at the non-serving base station 706 due to the mobile station 702 served by another base station 300 operating as the serving base station 704 for the mobile station 702. The non-serving base station 706 is included in the set of active base stations maintained by the mobile station 702. In the first exemplary embodiment, the coupled load indicator 710 represents the ECP / NT measured at the non-serving base station 706. In step 804, the serving base station 704 determines an expected coupled load 712 on the non-serving base station 706 due to mobile station 702 based on the coupled load indicator 710 and at least one transmission parameter. In the first exemplary embodiment, the serving base station 704 calculates the expected coupled load 712 for the mobile stations 702 expected to transmit in the next transmission based on the coupled load indicator 710 measured at the non-serving base station 706, the mobile station's scheduled transmission rate for the anticipated future transmission, and the mobile station 702's transmission power level. The expected coupled load, therefore, is the expected load for the non-serving base station 706 due to reverse link transmissions from mobile station 702 that includes at least the serving base station 704 and the non-serving base station 706 in the mobile station's list of active base stations. In step 806, the expected coupled load 712 is routed to base station 300, functioning as the non-serving base station 706 for mobile station 702. In the first exemplary embodiment, the expected coupled load 712 represents the expected load as a function of the scheduled transmission data rate and the expected ECP / Nt level at the non-serving base station 706 due to a planned future transmission from mobile station 702. However, the expected coupled load 712 may represent other parameters or values. For example, the expected coupled load 712 may represent an anticipated change in the load experienced at the non-serving base station 706 due to a future transmission from mobile station 702 compared to a previous transmission. In the first exemplary embodiment, the expected coupled load indicator 712 is formatted according to the appropriate protocol and transmitted through the return transport channel 208 of communication system 100.The expected coupled load indicator 712 can be routed to the non-serving base station 706 using other techniques. For example, a direct communication link between the serving base station 704 and the non-serving base station 706, such as a point-to-point microwave link, can be used to conduct the expected coupled load. Figure 9 is a flowchart of a method for determining available capacity at a base station 300 operating as a non-serving base station 706 according to the first exemplary embodiment of the invention. In some circumstances, the method described in Figure 9 is performed at a base station 300 that is also operating as a serving base station 704 for other mobile stations 110 to 114. The method described with reference to Figure 9 is performed when the set of active base stations maintained at at least one mobile station 702 includes the non-serving base station 706 and a serving base station 704.The techniques described here can be applied to any number of base stations (300) and mobile stations (110 to 114). In step 902, an expected coupled load 712 is received from a base station 300 operating as a server base station 704 of a mobile station 702 that maintains a set of active base stations that includes at least the non-server base station 706 and the server base station 704. As discussed above, the expected coupled load 712 represents the expected coupled load that will likely be experienced at the non-server base station 706 due to a future anticipated transmission from mobile station 702. In step 904, base station 300, functioning as non-serving base station 706, determines the available capacity at non-serving base station 706 based on the expected coupled load 712. After taking into account voice reverse and unscheduled traffic data, non-serving base station 706 determines the available capacity by calculating the difference between the total capacity and the sum of all expected loads and coupled loads. The remainder indicates the available capacity of non-serving base station 706 that can be used for mobile stations 110 to 114, for which non-serving base station 706 may be serving as a serving base station. In step 906, base station 300, functioning as non-serving base station 706, allocates reverse link channel resources 212 (programs the load) from mobile stations 110 to 114 served by base station 300, functioning as non-serving base station 706, to mobile station 702 according to available capacity. Non-serving base station 706 allocates available capacity by limiting power levels and data rates of any mobile stations 110 to 114 being served by non-serving base station 706. In the exemplary embodiment, the methods described with reference to Figure 8 and Figure 9 are performed within several geographically distributed 300 base stations, where any one of the 300 base stations, at any given time, may be functioning only as a 704 serving base station, only as a 706 non-serving base station, or both as a 704 serving base station for one or more 110 to 114 mobile stations and a 706 non-serving base station for one or more other 110 to 114 mobile stations. Furthermore, a 702 mobile station may maintain a set of active base stations that includes several 706 non-serving base stations in addition to the 704 serving base station.Therefore, to efficiently manage reverse link loads on the various base stations 300, the coupled load indicators 710 and expected coupled loads 712 are conducted to the appropriate base stations 300, and calculations are performed taking into account the various parameters received from multiple base stations 300. Figure 10 is a flowchart for allocating reverse link channel resources in a communication system 100 having geographically distributed base stations 300 according to the first exemplary embodiment of the invention. As described above, the functions of the server base stations 704 and non-server base stations 706 can be performed in a single base station 300 that functions as a server base station 704 for some mobile stations 110 to 114 and as an active non-server base station 706 for other mobile stations 114. In step 1002, base stations 300 operating as server base stations 704 receive coupled load indicators 710 measured at base stations 300 operating as non-server base stations 706, wherein the coupled loads are due to reverse link transmissions from mobile stations 702 served by the server base stations 704 and which maintain a set of active base stations that includes one or more of the non-server base stations 706. Each non-server base station 706 generates a coupled load indicator 710 which, together with the transmission rate, represents the coupled load measured at the non-server base station 706 due to mobile stations that are served by another base station 300. The coupled load indicators 710 are transmitted by the non-server base stations 706 to the corresponding server base station 704 via the return transport channel 708. A suitable notation for characterizing and describing the relationships between the various base stations 300, 704, 706 includes the use of subscripts to denote a set of base stations. In the first exemplary embodiment, each base station (BSj) that is in the active set of mobile stations (MSi), except when BSj and ServingBS_MSi, measures and transmits (Ecp / Nt)ji to the serving base station for the MSi. In the first exemplary embodiment, (Ecp / Nt)ji is used as a load-coupled indicator. ServingBS—MSi is the set of serving base stations for mobile stations (i) and (Ecp / Nt)ji(1 + (T / P)(Ri) + (C / P)) / (l + (Ecp / Nt)ji(l + (T / P)(Ri) + (C / P))) is the coupled load experienced on non-serving base stations (BSj) due to mobile stations (MSi) served by serving base stations. (T / P)(Ri) is the traffic / pilot ratio of the traffic channel when the transmission rate is Ri. (C / P) is the total sum of the power ratios of the control channels (and fundamental channels) / pilot power.In the exemplary mode, a value representing the (Ecp / Nt)ji is transmitted to the server base stations (BSk). In step 1004, each server base station 704 identifies the mobile stations 702 served by server base station 704 that are expected to transmit during a future transmission period. For each base station (BSk), the BSk determines a set (FSk) that includes the mobile stations served by the BSk that have a priority that exceeds a minimum priority. In step 1006, each serving base station 704 determines the expected coupled loads 712 for the non-serving base stations 706 due to the mobile stations 702 that the serving base station 704 is serving. The base station serving 704 determines the coupled load for each of the mobile stations 702 expected to transmit (i.e., which are members of the FSk set) based on the received coupled load indicators 710 received at the base stations serving 704 and the transmission parameters of the mobile stations 702. Thus, BSk determines the expected coupled loads for all MSi in the FSk at other BSj, where such BSj is ServingBS_MSi: where CoupleLoadkj is the total coupled load experienced at BSj due to the MSi served by BSk, is the estimated signal-to-interference ratio if the MSi receives a rate Ri on R-SCH, and is the total sum of control channel power (including the fundamental voice channel and the secondary pilot channel) to pilot channel power.is related to (Ecp / Nt)ji according to the following equation: where (T / P)(Ri) is the traffic / pilot power ratio when the transmission rate on the traffic channel scheduled by the serving base station is Ri. In step 1008, each of the 704 server base stations forwards the expected coupled load (CoupleLoadkj) to the 706 non-server base stations. The expected coupled loads 712 represent the expected coupled loads calculated by the 704 server base stations. Each base station (BSk) forwards CoupleLoadkj to all other base stations. In exemplary mode, the expected coupled loads 712 are transmitted through the return transport channel 208. In step 1110, each base station 300 functioning as a non-serving base station 706 for at least one mobile station 702 and receiving an expected coupled load 712 determines an available capacity of the non-serving base station 706 based on the expected coupled load 712. Since each of the non-serving base stations 706 can be a serving base station 704 for other mobile stations, each serving base station 704 receives a coupled load indicator from other serving base stations 704 if the particular serving base station 704 is also a non-serving base station 706.Therefore, each non-server base station 706 within BSk receiving a CoupledLoadjk determines the available capacity in BSk using the expression: where CoupledLoadjk is the sum of the coupled loads received from the other server base stations 704 and Cavk is the available capacity in the server base station 704 after taking into account all other load contributions from voice channel data traffic and the fundamental reverse channel. In step 1012, the server base stations 704, which are also functioning as non-server base stations 706, allocate reverse link channel resources to mobile stations 110 to 114 (i.e., schedule load for the mobile stations) according to the capacity available to the server base station 704. In the first exemplary embodiment, therefore, each server base station 704 that is also a non-server base station 706 schedules load from the MSi mobile stations that are served by the server base station 704, which also maintain other active base stations, according to the following equations: where CoupledoutLoadk is the scheduled load of all mobile stations with multiple base stations in the active set but served by the server base station. CoupledoutLoadkj is the same CoupledinLoadkj that was passed by BSk to BSj.Based on the remaining available capacity after mobile station programming, BSk server base stations allocate reverse channel resources to mobile stations that maintain only the server base station as the sole active base station. Therefore, according to the first exemplary embodiment of the invention, each base station 300 that is a member of a set of active base stations of a mobile station 702 measures and forwards the coupled loads due to those mobile stations 702 served by other base stations 704 to the serving base stations 704 of the mobile station 702. Each serving base station 704 calculates an expected coupled load 712 for those mobile stations 702 served by the calculating base station 704 and maintaining other active base stations. Each serving base station 704 calculates an available capacity based on the expected coupled loads received from other base stations 300 that are functioning as serving base stations 704 for other mobile stations.Thus, each base station 300 determines the available capacity based on the expected coupled loads calculated by the other base stations serving the mobile stations that contribute to the total load on base station 300. Resources are efficiently allocated without the use of a central controller, thereby minimizing delays and reducing the probability of retransmissions and lost data. Figure 11 is a block diagram of a part 1100 of a communication system 100 according to the second exemplary embodiment of the invention. For clarity, Figure 11 includes blocks representing two mobile stations 1102 and two active base stations 1104, 1106, including a serving base station 1104 and an active non-serving base station 1006.Those skilled in the art will note, based on the present teachings and known techniques, that a base station can function as a serving base station 1104 for several mobile stations 1102 and that any mobile station 1102 can maintain any number of active base stations 1104, 1106. The teachings described herein, therefore, can be extended to any number of mobile stations 1102, serving base stations 1104, and non-serving base stations 1006. The serving base station 1104 can be the first base station 102, the second base station 104, or the third base station 106 described above with reference to Figures 1 to 4. The serving base station 1104 can also function as an active non-serving base station 1106 for another mobile station (not shown in Figure 11) and the non-serving base station 1106 can function as a serving base station for other mobile stations (not shown in Figure 11). 11).Therefore, a base station can function simultaneously as a server base station 1104 for some mobile stations and as an active non-server base station 1106 for other mobile stations 1102. The functions described here for each of the base stations 1104, 1106, are therefore simultaneously performed by the other base stations 1104, 1106, in most circumstances. In a second exemplary embodiment, a base station 300 operating as a non-serving base station 1106 determines the maximum tolerable coupled load for mobile stations 1102 served by another base station operating as the serving base station 1104. Based on the total capacity of the non-serving base station 1106 and the load due to other mobile stations (not shown) served by the non-serving base station 1106, the non-serving base station 1106 determines a maximum tolerable coupled load due to mobile station 1102 not served by the non-serving base station 1106. In the second exemplary embodiment, the non-serving base station 1106 reserves capacity for mobile stations that have some other base stations 1104 as serving base stations. Non-serving base station 1106 determines the maximum tolerable coupled load that mobile stations 1102 served by base station 1104 can contribute to the total load on non-serving base station 1106.The non-serving base station 1106 then forwards the total sum of maximum tolerable coupled loads 1112 to all mobile stations 1102 served by the serving base station 1104 that maintain the non-serving base station 1106 in their active base station sets. The non-serving base station 1106 determines a coupled load indicator for each mobile station 1102. The coupled load indicators 1110 represent the estimated traffic quality measured at the non-serving base stations due to reverse link transmissions from the mobile stations 1102. In CDMA systems with a power-controlled pilot channel, an average and expected long-term pilot SNR constitutes an adequate coupled load indicator. The serving base station 1104 allocates reverse link resources to the mobile stations 1102 according to the maximum tolerable coupled load.In the second exemplary embodiment, the server base station 1104 allocates reverse link resources according to two sets of constraints. The first set of constraints is imposed by the capacity of the server base station 1104 and requires that the transmission data rate allocated to mobile stations 1102 must create a load on the server base station 1104 that is less than the available capacity on the server base station 1104. The second set of constraints is imposed by the maximum tolerable coupled load 1112 reported by the non-server base stations 1104. The rate allocated by the server base station 1104 to all mobile stations 1102 with the non-server base station 1106 in their active sets must create a load on the non-server base station 1106 that is less than the maximum tolerable coupled load.The load-coupled indicators 1110 and the allocated transmission data rate determine the expected load contributed by mobile station 1102 to the non-serving base station 1104. Figure 12 is a flowchart of a method for managing reverse link channels performed on a base station 300 operating as a serving base station according to the second exemplary embodiment of the invention. In some circumstances, the method described in Figure 12 is performed on a base station 300 that is also operating as a non-serving base station 1106. The method described with reference to Figure 12 is performed when at least one non-serving base station 1106 is maintained in the active base station set of at least one mobile station 1102 that is being served by the serving base station 1104. The techniques described herein can be applied to any number of base stations 300 and mobile stations 1102. In step 1202, a base station 300 functioning as the server base station 1104 receives a maximum tolerable coupled load 1112 representing a maximum tolerable coupled load on another base station 300 serving as a non-server base station 1106 for a mobile station 1102. The maximum tolerable coupled load 1112 is determined by the non-server base station 1106 based on priority requests and service rate from mobile stations served by the non-server base station 1106. In step 1204, a load-coupled indicator 1110 is received at the serving base station 1104. In exemplary mode, the load-coupled indicator 1110 is based on load-coupled parameters measured at the non-serving base station 1106 and represents a traffic channel quality measured at the non-serving base station 1106 due to reverse link transmissions 210 from the mobile station 1102 served by the serving base station 1104. In step 1206, the server base station 1104 manages the reverse link transmissions of mobile station 1102 according to the maximum tolerable coupled load 1112. In exemplary mode, the server base station 1104 calculates the expected coupled loads of all mobile stations 1102, keeping the non-server base station 1106 in its set of active base stations. Using the coupled load indicator 1110 for each mobile station 1102 and the mobile station transmission parameter of each mobile station 1102, the server base station 1104 calculates the expected coupled load for mobile station 1102. The server base station 1104 schedules data transmission rates for mobile stations 1102 such that the total expected coupled load on the non-server base station 1106 does not exceed the maximum tolerable coupled load 1112 during a future transmission.Therefore, the server base station 1104 allocates resources to the mobile stations 1102, conforming to the limits provided by the non-server base stations 1106, thus minimizing the probability of an overload condition in the non-server base stations 1106. Figure 13 is a flowchart of a method for managing reverse link channel resources in a base station 300 functioning as a non-server base station 1106 according to the second exemplary embodiment of the invention. In step 1302, base station 300, functioning as a non-server base station 1106 for mobile station 1102, forwards a load-coupled indicator 1110 to another base station 300, functioning as a server base station 1104 for mobile station 1102. This indicator is based on load-coupled parameters measured at non-server base station 1106 due to reverse link transmissions from mobile station 1102. In step 1304, the non-serving base station 1106 determines the maximum tolerable coupled load. Several mobile station rate requests are arranged in descending order of their priorities. After the mobile stations with the highest priorities are allocated capacity, mobile stations 1102 receive a capacity such that a certain fraction of the maximum tolerable coupled load equals the capacity reserved for mobile stations 1102. In step 1306, a maximum tolerable coupled load 1112 representing the maximum permissible load is routed to base station 300 functioning as the server base station. In the second exemplary embodiment, the maximum tolerable coupled load 1112 is transmitted through the return transport channel 208 to the server base station 1104. Figure 14 is a flowchart of a method for allocating reverse link channel resources in a communication system 100 having geographically distributed base stations according to the second exemplary embodiment of the invention. As described above, the functions of the server base stations 1104 and non-server base stations 1106 can be performed within a single base station 300 that functions as a server base station 1104 for some mobile stations 110 to 114 and as an active non-server base station 1106 for other mobile stations 114. In step 1402, all base stations that are maintained in an active list of a mobile station 1102 that is served by another base station forward a load-coupled indicator 1110 to the other base stations 1104 that are serving the mobile stations 1102. The load-coupled indicators 1110 are based on load-coupled parameters measured at base station 1106. In the second exemplary embodiment, base station 1106 measures and forwards the Ecp / Nt values ​​due to reverse link transmissions from mobile stations 1102 served by the other base stations 1104 that maintain base station 1106 in the active base station set. A suitable notation for characterizing and describing the relationships between the various base stations 300, 1104, 1106 includes the use of subscripts to denote a set of base stations. In the second exemplary embodiment, each base station (BSj) that is in the active set of mobile stations (MSi), except when BSj and ServingBS—MS}, measures and transmits the (Ecp / Nt) ji to the serving base station for the MSi. In the second exemplary embodiment, (Ecp / Nt)ji is used as a coupled load indicator 1110. ServingBS_MSi is the set of serving base stations for mobile stations (i) and (Ecp / Nt)ji(1+(T / P)(Ri)+(C / P)) / (1+(Ecp / Nt)ji(1+(T / P)(Ri)+(C / P))) is the coupled load experienced on non-serving base stations (BSj) due to mobile stations (MSi) served by the serving base stations. (T / P)(Ri) refers to the traffic / pilot ratio of the traffic channel when the transmission rate is Ri.(C / P) refers to the total sum of the power ratio of the control channels (and fundamental channel) / pilot power. In exemplary mode, a value representing (Ecp / Nt)ji is transmitted to the server base stations (BSk). In stage 1404, base stations 300, functioning as server base stations 1104, receive load-coupled indicators from base stations 1106 maintained in the active base station set by mobile stations served by base stations 1104. In step 1406, the base stations determine a maximum tolerable coupled load 1112 due to mobile stations served by other base stations based on the requests and priorities of mobile stations served by the base stations. A scheduling function in each base station j acting as a non-serving base station reserves the maximum tolerable coupled load capacity 1112 (MaxTolerableCoupledLoad jk) for mobile stations served by other base stations. In step 1408, the base stations pass on the maximum tolerable coupled load to the other base stations. Thus, each base station functioning as a non-serving base station passes on the maximum tolerable coupled load capacity 1112 (MaxTolerableCoupledLoad jk) to the serving base stations k. In stage 1410, the base stations functioning as serving base stations receive the maximum tolerable coupled loads 1102 originating from the non-serving base stations 1106 maintained in the set of active base stations of the mobile stations 1102 served by the base stations. In step 1412, the base stations calculate the available capacity at the base station for the mobile stations served by the base stations operating as a non-serving base station 1106 for some mobile stations and as a serving base station 1104 for other mobile stations. After reserving capacity for all mobile stations 1102 served by other base stations, the base stations operating as the non-serving base stations j calculate their available capacity according to the following equation: where Cavj is the available capacity at the non-serving base station j for scheduling the mobile stations for which base station j is the serving base station.The factor f represents how conservative base station j is in reserving capacity for mobile stations that it is not responsible for scheduling. f = 0 represents the case where base station j does not reserve any capacity for mobile stations that it is not scheduling, while f = 1 represents the case where base station j is more conservative. In step 1414, base stations manage reverse link transmissions by allocating reverse link resources according to the maximum tolerable coupled loads 1112 received from other base stations. In the second exemplary embodiment, base stations k allocate reverse link resources by allocating transmission data rates to all mobile stations i served by base stations k according to the following criteria: where CoupledLoad and Sinr are as defined above with reference to the first exemplary embodiment. Thus, each base station determines the coupled loads at the base station due to mobile stations served by other base stations, reserves capacity for such mobile stations, forwards the maximum tolerable coupled loads to all serving base stations that serve such mobile stations, and allocates reverse link resources based on the capacity available to mobile stations that the base station is serving and the maximum tolerable coupled loads received from non-serving base stations of the mobile stations served by the base station. Figure 15 is a block diagram of a part 1500 of a communication system 100 providing communication services to mobile stations 110 to 114 with geographically distributed base stations 102 to 108 according to the third exemplary embodiment of the invention.In most cases, the 100 communication system includes several 1504, 1506 base stations, which are strategically positioned to provide wireless communication services to various 1502 mobile stations. Depending on the quality of the communication channels between a 1502 mobile station and the base station (1504, 1506), the 1502 mobile station may be communicating with more than one base station (1504, 1506) at any given time. As mentioned above, each 1502 mobile station maintains a set of active base stations where the communication links between the 1502 mobile station and the active 1504, 1506 base stations are adequate for communication. Among the active base stations, one base station functions as the 1504 server base station, while the other base stations in the active set are non-server 1506 base stations.Such situations typically occur during a soft handoff where a single base station performs the functions of a server base station 1504 and one or more other base stations are active non-server base stations 1506. When conditions permit, the role of the server base station 1504 is transferred to a base station previously functioning as an active non-server base station 1506 (i.e., a handoff occurs). For clarity, Figure 15 includes blocks representing a mobile station 1502 and two active base stations 1504, 1506, including a serving base station 1504 and a non-serving base station 1506. Those skilled in the art will note, based on the present teachings and known techniques, that a base station 300 can function as a serving base station 1504 for multiple mobile stations 1502 and that any mobile station 1502 can maintain any number of active base stations 1504, 1506. The teachings described herein, therefore, can be extended to any number of mobile stations 1502, serving base stations 1504, and non-serving base stations 1506. As will be described in greater detail later, the other base stations 300 may not have a communication link with the mobile station 1502 of sufficient quality to become an active base station, but they can contribute to the load experienced on any of the base stations. active 1504, 1506.The base station 1504 may be the first base station 102, the second base station 104, or the third base station 106, described above with reference to Figures 1 to 4. The base station 1504 may also function as a non-serving base station 1506 for another mobile station (not shown in Figure 15), and the non-serving base station 1506 may function as a base station 1504 for other mobile stations (not shown in Figure 15). Thus, a base station 102 to 108 may simultaneously function as a base station 1504 for some mobile stations 1502 and as a non-serving base station for other mobile stations. The functions described here for each of the base stations 1504 and 1506 are therefore performed simultaneously by the other base station in most circumstances. In the third exemplary embodiment, a base station 300 operating as a non-serving base station 1506 estimates an expected coupled load 1508 due to mobile stations 1502 served by other base stations 1504 and allocates reverse link resources according to the expected coupled load 1508. Therefore, no direct or explicit communication is sent through a return transport channel 208 between the serving base station 1504 and the non-serving base station 1506 in the third exemplary embodiment of the invention. The serving base station 1504 schedules all the mobile stations 1502 that it is serving based on the channel quality of the traffic channel received at the serving base station 1504.Non-serving base station 1506 schedules the mobile stations (not shown) served by non-serving base station 1506 after estimating the expected coupled load 1508 contributed by all mobile stations 1502 that it is not scheduling (i.e., serving) but which are transmitting reverse link signals 210 that are received and processed by non-serving base station 1506. In some circumstances, the estimates of the expected coupled loads 1508 by non-serving base stations 1506 are based on measurements taken from previous transmissions of mobile stations 1502 in a soft handoff with non-serving base station 1506. The estimate includes the total expected coupled loads from all mobile stations 1502 for which 1506 is a non-serving base station 1506 and which are served by any other base station.Figure 16 is a flowchart of a method, implemented at a base station 300, for managing reverse link resources in a communication system 100 having geographically distributed base stations according to the third exemplary embodiment of the invention. In step 1602, a non-serving base station 1506 measures at least one coupled load parameter due to reverse link transmissions 210 from mobile stations 1502 served by other base stations 1504. In the third exemplary mode, during each transmission interval, the non-serving base station j measures the received pilot SNR ((Ecp / Nt)ji) and the transmission rate on the control and voice channels contributed by all MSi that have BSj in the Active Set, but are not programmed by BSj. Based on (Ecp / Nt) ji and the transmission rate Ri, the total coupled load (TotCoupledLoadj) during the current transmission (indexed by n) is computed according to the following equation: In step 1604, base station 1506 estimates the expected coupled load for a future transmission based on the measured total coupled load from at least one previous transmission.Any of several techniques can be used to estimate the expected coupled load for a future transmission (TotCoupledLoadj[n+1]), and the particular technique depends on the type of communication system 100, the transmission structure of the reverse links 210, 212, and other factors. One suitable technique includes using the measured TotCoupledLoadj[n] as the expected value for TotCoupledLoadj[n+1]. Another technique includes calculating a filtered average value (Exp_TotCoupledLoadj) to estimate TotCoupledLoadj[n+1] as specified by the following equation: is the filtering length. Signal processing schemes can be employed to estimate the cq coefficients. Furthermore, the oq coefficient can be adaptively modified to minimize the mean squared error between the estimated TotCoupledLoadj[n+1] and the actual measured TotCoupledLoadj[n+1] at time n+1. . Therefore, a total coupled load due to reverse link transmissions 210 from mobile stations served by other base stations is determined for at least one previous transmission. The estimated expected coupled load is based on previous total coupled loads and can be set equal to one of the previous coupled loads, or it can be determined by processing a plurality of coupled loads for previous transmission periods. Other techniques may be used in some circumstances to determine the estimated expected coupled load based on previous coupled loads. In hybrid ARQ systems with reverse link transmissions, a packet is transmitted through multiple transmissions until it is successfully received. If the delay between the first and subsequent transmissions remains fixed, the transmission line of a packet and its subsequent retransmissions is referred to as an ARQ occurrence. Due to retransmissions, a strong correlation can exist between the coupled load during subsequent ARQ occurrences. To take advantage of this correlation, Total Coupled Load can be estimated from previous transmissions during the same ARQ occurrence. In step 1606, the base station manages the reverse link transmissions 210 of the mobile stations served by the base station according to the estimated expected coupled load 1508. In the third exemplary embodiment, the non-serving base station j, after determining the estimated expected coupled load Est_TotCoupledLoadj[n+1], actuaJizes the available capacity for scheduling the mobile stations that have base station j as the serving base station according to the following equation: The base stations j allocate the reverse link resources in such a way that the total available capacity is not exceeded in the third exemplary embodiment.Thus, the base stations, functioning as non-serving base stations 1506 in the third exemplary embodiment, estimate an expected coupled load due to all mobile stations 1502 served by other base stations 1504 and allocate reverse link resources to the mobile stations served by the non-serving base station 1506 based on the total remaining capacity at the base station after taking into account the total expected coupled load. Naturally, other embodiments and modifications of the present invention will readily occur to those skilled in the art in light of the present teachings. The above description is illustrative and not restrictive. The present invention should be limited only by the following claims, which include all such embodiments and modifications when considered in conjunction with the above descriptive report and the accompanying drawings. The scope of the invention should therefore be determined not with reference to the above description, but rather with reference to the appended claims together with their full scope of equivalences. CLAIMS

Claims

1. A method implemented at a base station (102-108) functioning as a non-serving base station for at least one mobile station served by another base station, to allocate reverse link resources to mobile stations served by the base station in a distributed base station communication system, comprising: measuring load-coupled parameters of reverse link transmissions from at least one mobile station served by another base station; the method characterized in that it further comprises: calculating an estimated expected load-coupled due to reverse link transmissions from at least one mobile station based on the load-coupled parameters;allocate reverse link resources to other mobile stations served by the base station according to the estimated expected coupled load, wherein the allocation of reverse link resources comprises scheduling data transmission rates for the other mobile stations served by the base station to create a total reverse link load due to the other mobile stations at the base station not exceeding a difference of the total capacity of the base station and the estimated expected coupled load; wherein the estimate comprises calculating a prior coupled load due to reverse link transmissions from at least one mobile station based on coupled load parameters measured during a prior transmission period, the calculation of the prior coupled load comprising calculating the estimated expected coupled load;and calculate the estimated expected coupled load based on the previous coupled load, where calculating the estimated expected coupled load based on the previous coupled load includes calculating the estimated expected coupled load to be equal to the previous coupled load.

2. Method, according to claim 1, characterized in that the measurement of the coupled charge parameters comprises measuring an energy-per-chip / noise plus interference ratio (Ecp / Nt).

3. Method according to claim 2, characterized in that the calculation of the estimated expected coupled load further comprises calculating the estimated expected coupled load based on a data rate of reverse link signals transmitted by at least one mobile station.

4. Method according to claim 2, characterized in that the calculation of the estimated expected coupled load further comprises calculating the estimated expected coupled load based on a transmission power level of reverse link signals transmitted by at least one mobile station.

5. Method performed at a base station (102-108) in a distributed base station communication system, comprising: measuring coupled load parameters of reverse link transmissions from mobile stations served by other base stations; the method characterized in that it further comprises: calculating a total coupled load for a previous transmission period based on the coupled load parameters, the total coupled load representing a total load contribution due to reverse link transmissions from mobile stations; calculating an estimated expected coupled load for a current transmission based on the total coupled load; calculating a total available capacity of the base station by subtracting the estimated expected coupled load from a total capacity of the base station;and allocate reverse link resources to other mobile stations served by the base station according to the total available capacity, wherein the allocation of reverse link resources comprises scheduling data transmission rates for the other mobile stations served by the base station to create a total reverse link load due to the other mobile stations at the base station not exceeding the total available capacity of the base station, wherein the calculation of the estimated expected coupled load comprises calculating the estimated expected coupled load to be equal to the previous coupled load, wherein the calculation of the previous coupled load comprises calculating a plurality of previous coupled loads, and wherein the calculation of the estimated expected coupled load further comprises calculating a filtered average total expected coupled load from the plurality of previous coupled loads.

6. Method according to claim 5, characterized in that the measurement of the coupled charge parameters comprises measuring a chip energy / noise plus interference ratio (Ecp / Nt).

7. Method according to claim 6, characterized in that the calculation of the estimated expected coupled load for the current transmission further comprises calculating the estimated expected coupled load for the current transmission based on a data rate of reverse link signals transmitted by at least one mobile station.

8. Method according to claim 7, characterized in that the calculation of the estimated expected coupled load for the current transmission further comprises calculating the estimated expected coupled load for the current transmission based on a transmission power level of the reverse link signals transmitted by at least one mobile station.

9. Processor (304) for a base station (102 - 108) of a distributed base station communication system, characterized in that it is configured to: calculate a total coupled load due to reverse link transmissions from mobile stations (110 - 114) served by other base stations (102 - 108) for a previous transmission period based on the coupled load parameters measured at the base station (102 - 108); calculate an estimated expected coupled load for a current transmission period based on the total coupled load; calculate a total available capacity of the base station (102 - 108) by subtracting the estimated expected coupled load from a total capacity of the base station (102 - 108); allocate reverse link resources to other mobile stations (110 - 114) served by the base station (102 - 108) according to the total available capacity;Allocate reverse link resources by scheduling data transmission rates for the other mobile stations (110-114) served by the base station (102-108) to create a total reverse link load due to the other mobile stations (110-114) at the base station (102-108) not exceeding the total available capacity of the base station (102-108); calculate the estimated expected coupled load by calculating the estimated expected coupled load to be equal to the previous coupled load; calculate the total coupled load by calculating a plurality of previous coupled loads; and calculate the estimated expected coupled load by calculating a filtered average total expected coupled load from the plurality of previous coupled loads.

10. Processor (304), according to claim 9, characterized in that the load-coupled parameters comprise an energy-per-chip / noise plus interference ratio (Ecp / Nt).

11. Processor (304), according to claim 9, characterized in that it is additionally configured to calculate the estimated expected coupled load for the current transmission period based on a data rate of reverse link signals transmitted by at least one mobile station (110 - 114).

12. Processor (304), according to claim 9, characterized in that it is additionally configured to calculate the estimated expected coupled load for the current transmission period based on a transmission power level of reverse link signals transmitted by at least one mobile station (110 - 114).