Namsuk Lee

Performance Analysis of IEEE802.16d Random Access Protocol

In this paper, we investigate the performance of IEEE802.16d random access protocol based on orthogonal code-division-multiple-access and frequency-division-multiple-access in time division duplexing mode using equilibrium point analysis. The random access protocol of IEEE802.16d is similar to demand-assigned multiple access with piggyback, in which bandwidth request is allowed at the end of data transmission. In the analysis, we consider the retransmission probability derived from a binary exponential backoff algorithm. The performance is presented in terms of initial access delay, its throughput, message transmission delay and the system throughput with piggyback by varying number of subscriber stations, number of PN codes for bandwidth request ranging, number of slot-subchannel and the parameters of the binary exponential backoff algorithm.

An Efficient Multicast and Broadcast Service in IEEE 802.16e Wireless MANs

In IEEE 802.16e Wireless MANs providing multicast and broadcast service which an efficient method for concurrent transport of data common to a group of users. MBS_MAP message is proposed in order to alleviate MAP overhead for the multicast and broadcast service. However, it is not enough to resolve the MAP overhead problem. In this paper, we propose an efficient multicast and broadcast service in term of MAP overhead reduction. To achieve the purpose of MAP overhead reduction, a new indication of bitmap intended for one or multiple mobile stations is proposed. The indication indicates whether or not there is traffic addressed to one or multiple mobile stations. Our simulation results show that the proposed scheme provides better performance than that of legacy IEEE 802.16e Wireless MANs. Index Terms—IEEE 802.16, multicast and broadcast service (MBS), Wireless MANs

A contention based uplink scheduling request method in LTE-A

In this paper, a contention based uplink scheduling request method is proposed to enable low transmission latency in LTE-A systems. The proposed method transmits a BSR message over PUCCH which includes uplink resource information required by the UE. On the other hand, in LTE-A systems, a positive signal for scheduling request is transmitted over PUCCH. Performance analysis results show that the proposed method can significantly reduce the delay for uplink data transmission compared to that of the uplink SR method in LTE-A systems.

An efficient negative acknowledgment method for CDMA-based ranging in IEEE 802.16 OFDMA systems

Ranging in IEEE 802.16 systems is used to synchronize an uplink or to request an uplink bandwidth. The base station sends a ranging response message as a positive acknowledgment of a successfully received code. However, the base station does not provide a negative acknowledgment; hence, a mobile station is unable to determine if its ranging code is unsuccessfully transmitted. This paper proposes a negative acknowledgment method based on a ranging slot indicator and the frame number of a ranging response message. The results of the performance analysis show that the proposed method can reduce the delay of a code retransmission.