Instantaneous joint transmit power control and link adaptation for RTS/CTS based channel access

a power control and transmit power technology, applied in power management, wireless communication, data switching networks, etc., can solve the problems of harmful interference peaks of data reception, unfavorable distribution channel access, and power control not supported in known rts-cts based channel access schemes, etc., to improve the overall system performan

Inactive Publication Date: 2008-03-27
TELEFON AB LM ERICSSON (PUBL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0026] Exemplary embodiments of the invention take a more far-reaching transmit power-control (TPC) approach than outlined IEEE 802.11 TGh, and have the objective of improving the overall system performance in IEEE 802.11a as well as other RTS-CTS based channel access scheme to the greatest feasible extent In doing so, this will implicitly address QoS goals considered in IEEE 802.11 TGe.

Problems solved by technology

However, power control is not supported in known RTS-CTS based channel access schemes.
With respect to DBTMA with TPC, BTMA (Busy Tone Multiple Access) as such is generally not a viable solution for distributed channel access as it is extremely unpractical.
Also, control messages use maximum Transmit Power (TP), and therefore it is not possible for control messages to share a channel with data traffic as that would cause harmful interference peaks for data reception.
Another drawback is that information regarding fixed TP is assumed known at the receiver.
Another drawback is that asymmetries in interference, link gain, or TP capabilities are not been considered.
There are also additional problems common to each of general RTS-CTS, IEEE 802.11 and DBTMA, namely a) link adaptation has not been considered in the RTS-CTS framework, and b) asymmetries in terms of link adaptation capabilities have not been considered.

Method used

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  • Instantaneous joint transmit power control and link adaptation for RTS/CTS based channel access
  • Instantaneous joint transmit power control and link adaptation for RTS/CTS based channel access
  • Instantaneous joint transmit power control and link adaptation for RTS/CTS based channel access

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first embodiment

[0067] In Tier 2, relating to RTS, CTS and TPC, two major embodiments or cases exist. In the first embodiment, Fixed TPC, RTS / CTS are sent with the highest possible TP, but are limited by regulatory TP requirements. Hence the TP setting is identical to the Beacon information. The purpose of this embodiment is to be able to inform distant stations of ongoing DATA transmissions such that they can select DATA transmit parameters that will mitigate generation of disturbing interference. Although not supported by 802.11 per se, it should be noted that RTS / CTS frames could, in principle, be sent in a special control channel separated from data transmissions, hence avoiding interfering with said data transmissions.

[0068] In the second embodiment, Group TPC, the RTS and CTS are sent with a sufficiently high TP so as to reach members or stations within the same group / BSS, but preferably with a sufficiently low TP so as to a) not reach members within another group, and b) stay within regulato...

second embodiment

[0071] In a variant of the Tier 2 second embodiment, group based TPC is performed for the CTS message, while applying a lowest possible TP for the RTS frame. This primarily targets the case where the RTS-CTS phase can be housed within a single TS, i.e. not a IEEE 802.11a system. The motivation for this is that DATA reception is more vulnerable than the reception of ACKs, due to the potentially longer interference exposure time for the DATA frame.

[0072] In Tier 3, with respect to DATA, ACK TPC+LA, for DATA transmission an Instantaneous Closed Loop TPC and Instantaneous Closed Loop LA is deployed via feedback information conveyed in the CTS messages. In addition to this, DATA TPC also conforms to regulatory aspects as well as the RTS / CTS TPC setting. TPC and LA (Link Adaptation) for ACK generally follows the parameters for DATA. A special case is fragmented transmission when DATA and ACK headers acts as implicit RTS and CTS messages. Then the DATA, ACK and TPC may optionally become eq...

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Abstract

A method for closed loop link adjustment based on a Request To Send-Clear To Send (RTS-CTS) channel access scheme includes the following steps. Designating a station as an originating station. Transmitting a RTS frame with predetermined transmit power from an originating station, prior to an intended DATA transmission, sounding the channel such that reception characteristics can be evaluated at a designated receiving station. Transmitting, in response to the originating station, a CTS frame with a predetermined transmit power from the receiving station with directives of link adjustments. Transmitting a DATA frame from the originating station to the receiving station frame complying with link adjustment directives to the extent of the originating stations capabilities. And, transmitting an acknowledge (ACK) frame in response to the originating stations from the receiving station indicating result of DATA frame reception.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. application Ser. No. 10 / 117,128, filed Apr. 8, 2002, now pending, which claims the benefit of U.S. Provisional Application No. 60 / 282,191, filed on Apr. 9, 2001, the disclosure of which is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The invention relates to the field of wireless communications, in particular to transmit power control and link adaptation techniques and mechanisms. [0004] 2. Background Information [0005] The IEEE 802.11 is a wireless LAN (Local Area Network) standard that has been standardized by IEEE (Institute of Electrical & Electronics Engineers). The IEEE 802.11 wireless LAN standard is currently undergoing a process of extending the standard with QoS (Quality of Service) features. The objective is to enable, for example, computers or multimedia devices to communicate under QoS constraints. This standard extension goes u...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H04B7/00H04Q7/20H04B7/005H04B7/26H04L12/28H04L12/56H04W28/18H04W28/26H04W36/00H04W52/08H04W52/10H04W52/16H04W52/46H04W52/50H04W52/54
CPCH04W28/18H04W28/26H04W52/08H04W52/10H04W74/0816H04W52/46H04W52/50H04W52/54H04W52/16H04W52/243
Inventor LARSSON, PETER
Owner TELEFON AB LM ERICSSON (PUBL)
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