COMMUNICATIONS NETWORK AND METHOD FOR OPERATING A COMMUNICATIONS NETWORK

Description

State of the art

[0001] In conventional communication networks, training sequences must be sent and evaluated in both directions to determine the channel properties. This leads to a reduction in the effective payload data rate in both directions, since no payload data can be sent during the transmission of these training sequences. Furthermore, it is possible that one frequency band is more disturbed than the other (e.g., more attenuated). With a static assignment of the frequency bands to the transmission directions (DL and UL), one of the two transmission directions would therefore, on average, be more disturbed. Since in many cases both transmission directions are equally important for the overall system, the overall performance is determined solely by the weaker channel.

[0002] EP 1 730 858 B1 discloses a method, apparatus, and system for duplex communication. Uplink and downlink frequencies are assigned orthogonally, such that at one time a particular carrier frequency is used for uplink (downlink) transmission and at another time for downlink (uplink) transmission. Accordingly, at this one time a second carrier frequency is used for downlink (uplink) transmission and at this other time selectively for uplink (downlink) transmission.

[0003] US 2011 / 0116432 A1 discloses a method comprising using a first frequency for communication in a first direction with an infrastructure node and a second frequency for communication in a second direction with the infrastructure node during a normal operation phase in a wireless network. The method may further comprise reversing the frequencies used for communication in the first and second directions with the infrastructure node during a link reversal phase. Disclosure of the invention

[0004] The problem underlying the invention is solved by a communication network according to claim 1.

[0005] A first aspect of this description relates to a first communication module for a communication network, wherein the first communication module comprises at least one processor and at least one memory, wherein the processor and the memory are configured such that the first communication module transmits a first known sequence and first data on a first duplex channel within a first time frame, receives second data on a second duplex channel within the first time frame, wherein the reception of the second data is performed simultaneously with the transmission of the first a-priori known sequence and / or the first data, receives third data on the first duplex channel within a second time frame following the first time frame, and transmits a second a-priori known sequence and fourth data on the second duplex channel within the second time frame,wherein the transmission of the second a-priori known sequence and / or the fourth data is carried out simultaneously with the reception of the third data.,

[0006] This advantageously means that channel estimates are only required on the side of the other communication partner, for example a second communication module. The a priori known sequence(s) only need to be transmitted in one transmission direction (e.g. in the downlink), since the channel does not need to be estimated in the corresponding other transmission direction. Instead, the reciprocity of a radio channel can be advantageously exploited (i.e. the channel behaves exactly the same in both transmission directions). For example, the channel estimates determined for receive-side equalization can subsequently also be used for transmitter-side pre-distortion of a signal on the same transmission resources. This results in a whole series of advantages: A reduction in the overhead due to transmission orEmbedding known training sequences into the data stream, thereby increasing the net / useful data rate, increasing the energy efficiency of devices by reducing the number of required channel estimates, and reducing the signaling overhead that would be necessary without the proposed method to inform the transmitter of the channel estimates determined at the receiving end. By continuously switching duplex channels, the same transmission quality is achieved on average in both transmission directions. In the event of severe interference in one frequency band, neither transmission direction fails completely. The overall performance is therefore no longer determined by the more severely disturbed transmission direction, but by the average performance in both transmission directions.

[0007] By reusing the a priori known sequence in both communication directions, a separate transmission of a training sequence for channel estimation in one direction can be eliminated. In the case of a radio communication network, it may not be possible to completely eliminate an uplink preamble, for example, to determine timing advance values. However, by omitting a training sequence, the proposed a priori known sequence can be shorter, which leads to an increase in the payload data rate in one communication direction.

[0008] In cases where one of the two duplex channels involved is significantly more disrupted than the other transmission channel, the proposed measures ensure that neither transmission direction will fail completely with a higher probability. Higher transmission availability is achieved in each direction at least every other cycle. Applications requiring high availability particularly benefit from this. This increases the robustness of communication through the diversity of the duplex channels used and their utilization.

[0009] An advantageous example is characterized in that the first communication module provides the received second data without a prior estimation of the second duplex channel, and provides the received third data without a prior estimation of the first duplex channel. Advantageously, an estimation of the duplex channels is omitted on the first communication module side, which is compensated for by predistortion on the communication partner side.

[0010] An advantageous example is characterized by the first communication module transmitting the first data without a prior estimation of the first duplex channel, and transmitting the fourth data without a prior estimation of the second duplex channel. Advantageously, the estimation of the duplex channels on the first communication module side and the corresponding predistortion during transmission are also eliminated, which is compensated for by an estimation and correction on the communication partner side.

[0011] An advantageous example is characterized in that the first and second duplex channels are physical radio channels, wherein the a priori known sequence, the first data and the fourth data are downlink data, and the second data and the third data are uplink data. Since terminal devices of a radio communication network are located at different locations, each duplex channel between the respective terminal device and an infrastructure-side network unit, such as a base station, has individual channel properties. These channel properties include, for example, individual channel attenuation and phase shift.For example, if it is required that all uplink signals transmitted by different end devices reach the infrastructure-side network unit synchronously and without channel distortion despite different channel characteristics, it follows that any compensation of the transmission channels must be performed on the end devices. This means that equalization is performed on the receiver side in the downlink direction and predistortion is performed on the transmitter side in the uplink direction. Consequently, only the corresponding channel estimates need to be available or determined on the end device side.

[0012] An advantageous example is characterized in that the first and the second duplex channel are physical radio channels, wherein the a priori known sequence, the first data and the fourth data are uplink data, and wherein the second data and the third data are downlink data.

[0013] A further aspect of this description relates to a method for operating a first communication module, the method comprising: transmitting a first a-priori known sequence and first data on a first duplex channel within a first time frame, receiving second data on a second duplex channel within the first time frame, wherein the reception of the second data is carried out simultaneously with the transmission of the first a-priori known sequence and / or the first data, receiving third data on the first duplex channel within a second time frame following the first time frame, and transmitting a second a-priori known sequence and fourth data on the second duplex channel within the second time frame, wherein the transmission of the second a-priori known sequence and / or the fourth data is carried out simultaneously with the reception of the third data.

[0014] A further aspect of this description relates to a second communication module for a communication network, wherein the second communication module comprises at least one processor and at least one memory, wherein the processor and the memory are configured such that the second communication module receives a first a-priori known sequence and first data on a first duplex channel within a first time frame, transmits second data on a second duplex channel within the first time frame, wherein the transmission of the second data is performed simultaneously with the reception of the first a-priori known sequence and / or the first data, transmits third data on the first duplex channel within a second time frame following the first time frame, and receives a second a-priori known sequence and fourth data on the second duplex channel within the second time frame,wherein the reception of the second a-priori known sequence and / or the fourth data is carried out simultaneously with the transmission of the third data.,

[0015] This achieves reduced overhead with respect to the a priori known sequence. The a priori known sequence sent by the first communication module can be advantageously used by the second communication module to equalize the received data in the current time slot and pre-distort the UL data in the subsequent time slot.

[0016] An advantageous example is characterized in that the second communication module determines a first estimate of the first duplex channel as a function of the received first a-priori known sequence, determines an estimate of the second duplex channel as a function of the received second a-priori known sequence, predistorts the second data to be transmitted on the basis of the second estimate of the second duplex channel, and predistorts the third data to be transmitted on the basis of the first estimate of the first duplex channel.

[0017] An advantageous example is characterized in that the second communication module determines the first estimate of the first duplex channel as a function of the received first a-priori known sequence, determines the estimate of the second duplex channel as a function of the received second a-priori known sequence, equalizes the received first data on the basis of the first estimate of the first duplex channel, and equalizes the received fourth data on the basis of the second estimate of the second duplex channel.

[0018] Advantageously, an estimation of the duplex channels on the side of the first communication module can be omitted, which is compensated by the predistortion on the side of the second communication module.

[0019] An advantageous example is characterized in that the first and the second duplex channel are physical radio channels, wherein the a priori known sequence, the first data and the fourth data are downlink data, and wherein the second data and the third data are uplink data.

[0020] Because end devices in a radio communication network are located at different locations, each duplex channel between the respective end device and an infrastructure-side network unit, such as a base station, has individual channel characteristics. These channel characteristics include, for example, individual channel attenuation and phase shift.

[0021] For example, if it is required that all uplink signals transmitted by different end devices reach the infrastructure-side network unit synchronously and without channel distortion despite different channel characteristics, it follows that any compensation of the transmission channels must be performed on the end devices. This means that equalization is performed on the receiver side in the downlink direction and predistortion is performed on the transmitter side in the uplink direction. Consequently, corresponding channel estimates only need to be available or determined on the end device side.

[0022] An advantageous example is characterized in that the first and the second duplex channel are physical radio channels, wherein the a priori known sequence, the first data and the fourth data are uplink data, and wherein the second data and the third data are downlink data.

[0023] Further aspects of this description relate to a terminal of a radio communication network, wherein the terminal comprises the first or second communication module according to one of the preceding aspects.

[0024] Further aspects of this description relate to an infrastructure-side network unit of a radio communication network, wherein the network unit comprises the first or second communication module according to one of the preceding aspects.

[0025] A further aspect of this description relates to a method for operating a second communication module, the method comprising: receiving a first a-priori known sequence and first data on a first duplex channel within a first time frame, transmitting second data on a second duplex channel within the first time frame, wherein the transmission of the second data is carried out simultaneously with the reception of the first a-priori known sequence and / or the first data, transmitting third data on the first duplex channel within a second time frame following the first time frame, and receiving a second a-priori known sequence and fourth data on the second duplex channel within the second time frame, wherein the reception of the second a-priori known sequence and / or the fourth data is carried out simultaneously with the transmission of the third data.

[0026] The drawing shows: Figure 1 shows a schematic representation of a radio communication network; Figure 2 shows a schematic representation of a sequence diagram; and Figures 3 and 4 each show a schematic switching scheme for duplex channels.

[0027] Figure 1shows an example of a cell-based bidirectional radio communication network CELL. The first wireless communication network CELL comprises a network infrastructure-side network unit BS, a first terminal UE1, and a second terminal UE2. The network infrastructure-side network unit BS comprises a communication module C1, which includes a processor P1 and a memory element M2. The network infrastructure-side network unit BS can also be referred to as a base station or eNodeB. The network infrastructure-side network unit BS is connected to a stationary antenna A1 in order to transmit data in a downlink direction DL and to receive data in an uplink direction UL. The antenna A1 comprises, for example, a number of antennas and is designed as a remote radio head (RRH). The network infrastructure-side network unit BS and the antenna A provide a cell C, within which the terminals UE1 and UE2 communicate with the network unit BS.Of course, the network infrastructure-side network unit BS can also be distributed within the framework of virtualization and consist of individual network units.

[0028] The terminal device UE1, UE2 each comprises a communication module C2, C3, which comprises a processor P2, P3 and a memory element M2, M3. The two terminal devices UE1, UE2 are located within cell C, receive data in the downlink direction DL and send data in the uplink direction UL. The communication modules C1 and C2, or C1 and C3, are coordinated so that communication takes place via a first duplex channel CH1 and a second duplex channel CH2. The two duplex channels CH1 and CH2 differ, for example, in the frequency range used. Both duplex channels are used in both the downlink direction DL and the uplink direction UL. Furthermore, additional duplex channels can be provided, which are used by the communication modules C1 to C3. The duplex channels CH1 and CH2 use different frequency bands, for example, in FDD (Frequency Division Duplex).

[0029] However, the methods and measures described below are not limited to use in radio communication networks. Naturally, other communication networks can also benefit from the described measures. For example, in other communication networks, physical transmission channels (e.g., frequency or space) differ from one another and can be used for both transmission directions. The measures described here can be used in a variety of bidirectional communication systems where channel estimation is necessary and where both the channel parameters and / or the channel quality are constantly changing. This is particularly important in a variety of radio communication applications, such as, for example, in Figure 1This is the case as shown. Furthermore, the method can be used in a variety of other bidirectional transmission methods that utilize full duplex, i.e., simultaneous transmission in both directions. In addition to FDD in wireless and wired communication networks, this also applies to systems that route transmission streams via individual spatial streams, e.g., via individual electrical or optical lines for each transmission direction. Provided the transmit and receive structures allow for continuous duplex channel switching, the advantages of reduced preamble and increased diversity can also be exploited here.

[0030] Figure 2shows a schematic sequence diagram for operating the communication network CELL. The network unit BS on the network infrastructure side determines a control message CNTRL in a step 202, which is transmitted to the terminal device UE1 in a step 204. The control message CNTRL includes instructions relating, for example, to the duplex channel switching schemes explained below. In a step 206, data N11 is determined for transmission to the terminal device UE1. In a step 208, data N12 is determined for transmission to the network unit BS.

[0031] In a step 209, the data N12 are pre-distorted depending on a previously performed channel estimation for the second duplex channel CH2, so that in the best case, the network unit BS does not have to perform a channel estimation and the associated channel equalization. In the first cycle when commissioning the radio connection, this step 209 is omitted because the terminal device UE1 has not yet determined a channel estimation for the channel CH2. In a step 210, an a priori known sequence S11 and the data N11 are transmitted to the terminal device UE1 via the first duplex channel CH1. In a step 212, the data N12 are transmitted from the terminal device UE1 to the network unit BS via the second duplex channel CH2. Steps 210 and 212 overlap temporally within a time window tf1.

[0032] Depending on the received pre-known sequence S11, the terminal UE1 determines an estimate of the channel CH1 in a step 214. Depending on the determined estimate of the channel CH1, the received data N11 is equalized in a step 216 and provided to an application of the terminal UE1.

[0033] In a step 218, the terminal device UE1 synchronizes itself to the received pre-known sequence S11. For example, based on a pre-known position of the pre-known sequence S11, the beginning of the time window tf1 and the beginning of the subsequent time window can be determined.

[0034] In a step 220, the data N12 are provided to an application of the network unit BS without a prior channel estimation or prior equalization of the data N12.

[0035] Time window tf1 is immediately followed by time window tf2. The steps shown around the time windows are executed in parallel to those in time windows tf1, tf2, or before or after them. It should be explicitly noted that this representation is merely schematic.

[0036] In a step 230, data N22 is determined to be sent to the terminal device UE1. In a step 232, data N21 is determined to be sent to the network unit BS. In a step 231, the data N21 is pre-distorted before transmission so that the data N21 arrives at the recipient, the network unit BS, with as little distortion as possible.

[0037] After the end of the time window tf1, the duplex channels CH1 and CH2 are switched for the DL and UL directions of communication. Consequently, during the time window tf2, a previously known sequence S21 and the data N22 are transmitted to the terminal device UE1 on the second duplex channel CH2 in a step 234. Overlapping with step 234, the data N21 is transmitted to the network unit BS on the first duplex channel CH1 in a step 236. The received data N21 is provided in a step 250.

[0038] Depending on the received known sequence S21, the terminal device UE1 determines an estimate of the channel CH2 in a step 244. Depending on the determined estimate of the channel CH2, the received data N22 is equalized in a step 246 and provided to an application of the terminal device UE1.

[0039] In a step 248, the terminal device UE1 synchronizes itself to the received known sequence S21. For example, based on a known position of the known sequence S11 within the time window, the beginning of the time window tf1 and the beginning of the subsequent time window tf2 can be determined.

[0040] The a priori known sequences S11 and S21 can be referred to as a preamble or pilot sequence. Furthermore, the sequences S11 and S21, as well as other sequences used, can be identical. Furthermore, it is also possible to arrange the sequences S11 and S21 in a different position than the one shown. The a priori known sequences are either fixed or are distributed to the terminals, for example, via the control message CNTRL.

[0041] In one example, step sequences 260 and 270 alternate, whereby the duplex channels CH1 and CH2 are used alternately for the communication directions DL and UL.

[0042] Of course, the provided steps can also be used in reverse. This means that channel estimation is always performed only on the infrastructure-side network unit, and the infrastructure-side network unit also always performs equalization and predistortion. Furthermore, the provided method can also be used when channel estimation is not based on the preamble, but rather on pilot signals embedded in the payload data, as is the case, for example, with OFDM-based communication systems. In this case, the transmission of corresponding pilot signals in one direction could even be dispensed with, which in turn advantageously increases the effective spectral efficiency.

[0043] Figure 3shows a schematic of the use of the two duplex channels CH1 and CH2. Data N11, N22, N31, and N42 are sent in the downlink direction to the end device, whereas data N12, N21, N32, and N41 are sent in the uplink direction to the infrastructure-side network unit.

[0044] Figure 4shows a schematic of the use of duplex channels CH1, CH2, and CH3, although additional duplex channels can also be used. For example, several narrowband duplex channels are available for transmission, which are switched between according to a defined pattern. This hopping sequence is known to both the transmitter and the receiver, for example, through prior signaling and synchronization. Frequency hopping has the advantage that an unauthorized receiver cannot successfully receive the transmission signal without knowledge of the hopping sequence. Furthermore, frequency hopping generally offers good transmission properties in the event of narrowband interference, since transmission is only impaired when the current transmission channel and the narrowband interference briefly coincide. The infrastructure-side network unit hops back and forth between more than two duplex channels in the downlink direction.After each channel change, an a priori known sequence S11, S21, S32 is sent for channel estimation. In the uplink, the end devices change duplex channels in the same order—although always delayed by one change compared to the downlink. If a duplex channel is used for the downlink in one cycle, it is used for the uplink in the next cycle. In this case, the channel estimate recorded in the downlink direction is advantageously only one cycle older when applied in the uplink.

Claims

1. Communication network comprising a first communication module (C1) and a second communication module (C2), wherein the first communication module (C1) comprises at least one processor and at least one memory, the processor and the memory being configured in such a way that the first communication module (C1) sends a first a priori known sequence (S11) and first data (N11) on a first duplex channel (CH1) within a first time frame (tf1), receives second data (N12) on a second duplex channel (CH2) within the first time frame (tf1) without an a priori known sequence, the receiving of the second data (N12) being performed at the same time as the sending of the first a priori known sequence (S11) and / or the first data (N11), receives third data (N21) on the first duplex channel (CH1) within a second time frame (tf2), which follows the first time frame (tf1), without an a priori known sequence, and sends a second a priori known sequence (S21) and fourth data (N22) on the second duplex channel (CH2) within the second time frame (tf2), the sending of the second a priori known sequence (S21) and / or the fourth data (N22) being performed at the same time as the receiving of the third data (N21), and wherein the second communication channel (C2) comprises at least one processor and at least one memory, the processor and the memory being configured in such a way that the second communication module (C2) receives the first a priori known sequence (S11) and first data (N11) on the first duplex channel (CH1) within the first time frame (tf1), sends second data (N12) on the second duplex channel (CH2) within the first time frame (tf1) without an a priori known sequence, the sending of the second data (N12) being performed at the same time as the receiving of the first a priori known sequence (S11) and / or the first data (N11), sends third data (N21) on the first duplex channel (CH1) within the second time frame (tf2), which follows the first time frame (tf1), without an a priori known sequence, and receives the second a priori known sequence (S21) and fourth data (N22) on the second duplex channel (CH2) within the second time frame (tf2), the receiving of the second a priori known sequence (S21) and / or the fourth data (N22) being performed at the same time as the sending of the third data (N21), wherein the second communication module (C2) ascertains a first estimation of the first duplex channel (CH1) on the basis of the received first a priori known sequence (S11), ascertains a second estimation of the second duplex channel (CH2) on the basis of the received second a priori known sequence (S21), wherein the first communication module (C1) provides the received second data (N12) without a previously performed estimation of the second duplex channel (CH2), provides the received third data (N21) without a previously performed estimation of the first duplex channel (CH1), sends the first data (N11) without a previously performed estimation of the first duplex channel (CH1), and sends the fourth data (N22) without a previously performed estimation of the second duplex channel (CH2), and the second communication module (C2) predistorts the second data (N12) to be sent, on the basis of a previously performed estimation of the second duplex channel (CH2), predistorts the third data (N21) to be sent, on the basis of the first estimation of the first duplex channel (CH1), equalizes the received first data (N11) on the basis of the first estimation of the first duplex channel (CH1), and equalizes the received fourth data (N22) on the basis of the second estimation of the second duplex channel (CH2).

2. Communication network according to Claim 1, wherein the first and second duplex channels (CH1, CH2) are physical radio channels, wherein the a priori known sequence (S11, S21), the first data (N11) and the fourth data (N22) are downlink data, and wherein the second data (N12) and the third data (N21) are uplink data.

3. Communication network according to Claim 1, wherein the first and second duplex channels (CH1, CH2) are physical radio channels, wherein the a priori known sequence (S11, S21), the first data (N11) and the fourth data (N22) are uplink data, and wherein the second data (N12) and the third data (N21) are downlink data.

4. Communication network according to Claim 1, wherein a network unit (BS) comprises the first communication module (C1).

5. Communication network according to Claim 1, wherein a terminal comprises the first communication module (C1).

6. Communication network according to Claim 1, wherein a terminal (UE1, UE2) comprises the second communication module (C2).

7. Communication network according to Claim 1, wherein a network unit comprises the second communication module (C2).

8. Method for operating a communication network having a first communication module (C1) and a second communication module (C2), wherein the method comprises: sending a first a priori known sequence (S11) and first data (N11) on a first duplex channel (CH1) within a first time frame (tf1) by means of the first communication module (C1), receiving, by means of the first communication module (C1), second data (N12) on a second duplex channel (CH2) without an a priori known sequence within the first time frame (tf1), the receiving of the second data (N12) being performed at the same time as the sending of the first a priori known sequence (S11) and / or the first data (N11), receiving, by means of the first communication module (C1), third data (N21) on the first duplex channel (CH1) without an a priori known sequence within a second time frame (tf2), which follows the first time frame (tf1), and sending a second a priori known sequence (S21) and fourth data (N22) on the second duplex channel (CH2) within the second time frame (tf2) by means of the first communication module (C1), the sending of the second a priori known sequence (S21) and / or the fourth data (N22) being performed at the same time as the receiving of the third data (N21), providing the received second data (N12) by means of the first communication module (C1) without a previously performed estimation of the second duplex channel (CH2), providing the received third data (N21) by means of the first communication module (C1) without a previously performed estimation of the first duplex channel (CH1), sending the first data (N11) by means of the first communication module (C1) without a previously performed estimation of the first duplex channel (CH1), and sending the fourth data (N22) by means of the first communication module (C1) without a previously performed estimation of the second duplex channel (CH2), and wherein the method further comprises: receiving, by means of the second communication module (C2), the first a priori known sequence (S11) and first data (N11) on the first duplex channel (CH1) within the first time frame (tf1), sending, by means of the second communication module (C2), second data (N12) on the second duplex channel (CH2) without an a priori known sequence within the first time frame (tf1), the sending of the second data (N12) being performed at the same time as the receiving of the first a priori known sequence (S11) and / or the first data (N11), sending, by means of the second communication module (C2), third data (N21) on the first duplex channel (CH1) without an a priori known sequence within the second time frame (tf2), which follows the first time frame (tf1), and receiving, by means of the second communication module (C2), the second a priori known sequence (S21) and fourth data (N22) on the second duplex channel (CH2) within the second time frame (tf2), the receiving of the second a priori known sequence (S21) and / or the fourth data (N22) being performed at the same time as the sending of the third data (N21), ascertaining, by means of the second communication module (C2), a first estimation of the first duplex channel (CH1) on the basis of the received first a priori known sequence (S11), ascertaining, by means of the second communication module (C2), a second estimation of the second duplex channel (CH2) on the basis of the received second a priori known sequence (S21), predistorting, by means of the second communication module (C2), the second data (N12) to be sent, on the basis of a previously performed estimation of the second duplex channel (CH2), predistorting, by means of the second communication module (C2), the third data (N21) to be sent, on the basis of the first estimation of the first duplex channel (CH2), equalizing, by means of the second communication module (C2), the received first data (N11) on the basis of the first estimation of the first duplex channel (CH1), and equalizing, by means of the second communication module (C2), the received fourth data (N22) on the basis of the second estimation of the second duplex channel (CH2).