A new CDMA-based bandwidth request method for IEEE 802.16 OFDMA/TDD systems

2013

IEICE ComEX

Contention-based bandwidth request (BR) mechanism in wireless networks is suggested for users with ad-hoc connectivity to support best effort services at affordable cost. In this letter, we develop failure aware contention mechanisms when message and code based signaling mechanisms are carried out on a link with three-hop. The stations perform contention with dynamic update of contention window from the model developed through appropriate failure events of a link. Attributes that influence the contention BR are analyzed through the developed model. The proposed model is validated by means of numerical results.

Section: Simulation Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Failure aware contention based bandwidth request for multihop relay networks

2013

IEICE ComEX

“…The contention based bandwidth request (BR) mechanisms in WiMAX networks are classified into message BR and code division multiple access (CDMA) or simply code BR [11]. There always exists a tradeoff between message and CDMA BR with single hop networks.…”

Section: Introductionmentioning

confidence: 99%

Investigation on Mutual Contention Bandwidth Request Mechanisms in Two-Hop Relay Network with ITU-R Path Loss Models

ISRN Communications and Networking

2013

The performance of two-hop contention based bandwidth request (BR) mechanism for WiMAX relay networks is investigated under ITU-R path loss models. In conventional WiMAX systems, the mobile stations (MS) update their contention window irrespective of their transmission failures. Those systems update their contention window on collision and due to channel error or unavailability of bandwidth. Further, these failure models have been suggested for single hop networks. The failure model in two-hop systems becomes complex since it may include additional failure events such as improper detection of codes and channel error due to varying path loss. Interestingly, these failure events (collision, channel error, unavailability of bandwidth, and improper detection of codes) do not occur evenly for both hops of a link. Hence, to set the contention window effectively, unique failure models are developed by considering the characteristics of BR mechanism and hop at which the BR is performed. In the proposed system, the two-hop BR is carried out with all combinations of message and code bandwidth request schemes. Among them, the messagecode BR mechanism performs better under suburban fixed and outdoor to indoor or pedestrian environment, and code-code BR scheme performs better for vehicular environment.

“…Accordingly, the WiMAX standard [1] defines contention resolution with message based bandwidth request [9][10][11] when orthogonal frequency division multiplexing (OFDM) is used as physical layer. Recently, the orthogonal frequency division multiple access (OFDMA) based physical layer in WiMAX supports both message based and code division multiple access (CDMA) based [2][3][4][5][6][7][8] bandwidth request. In this paper, the CDMA based bandwidth request is considered since it delivers high contention efficiency than message based bandwidth request.…”

Section: Introductionmentioning

confidence: 99%

Heuristic Contention Based Bandwidth Request for IEEE 802.16 Networks

2012 Spring Congress on Engineering and Technology

2012

In this paper, we suggest and investigate CDMA based contention resolution with base station assisted backoff (C-BAB) for orthogonal frequency division multiple access (OFDMA) based WiMAX networks. Previous research on contention resolution considered CDMA with mobile assisted TBEB (C-MAB) suffers low contention efficiency and high access delay due to the type of accessing mechanism in WiMAX network. Also it has limitations in estimating the contention window based on current channel status. With C-BAB, the BS estimates the optimum contention window by accounting average contention window with instantaneous probability of failure. The performance of WiMAX network in terms of contention efficiency and access delay is studied by varying number of stations and the number of ranging slots allocated for bandwidth request. The contention efficiency and access delay of C-BAB show an improvement of 23.87% and 33.20%, respectively, than C-MAB.