3/sup rd/ generation RACH transmission-a candidate

In this part of the paper, we investigate the throughput bound of CDMA unslotted ALOHA system with a hybrid type II automatic-repeat-request (ARQ) implemented using rate compatible punctured turbo codes. The system under consideration can be regarded as an enhanced version of the classical CDMA packet radio network. When applying a hybrid type-II ARQ, the probability of packet success and packet length is generally different from attempt to attempt. Since the conventional analytical model, customarily employed for the ALOHA system with pure or hybrid type-I ARQ, cannot be applied for this case, we introduce an expanded analytical model, which can be regarded as a network of queues, and apply Jackson and Burke's theorems to simplify the analysis. When using code combining, soft-decision decoding is usually considered, in which case, it is very difficult to find the actual probability of packet success, especially when the number of terminals changes during a packet time duration. Hence, instead of finding the actual probability of packet success, we evaluate a lower and an upper bound. Together with the expanded model and the packet success probability bound, we obtain the corresponding throughput bounds by iteratively searching the steady-state arrival rate, , and the average departure rate, , for given composite offered traffic, = . The results show that significant improvement in throughput can be achieved by exploiting high coding gain of turbo codes and channel utilization efficiency of incremental redundancy retransmission protocol.Index Terms-ALOHA, code-division multiple-access (CDMA), hybrid automatic-repeat-request (ARQ), packet radio, rate compatible punctured codes and throughput, turbo codes.

Section: Numerical Resultsmentioning

confidence: 99%

Section: B Lower Bound On Packet Success Probabilitymentioning

confidence: 99%

Section: Threshold Effect and Channel Load Sensing Protocolmentioning

confidence: 99%

See 1 more Smart Citation

Packet Data Communications Over Coded CDMA—Part II: Throughput Bound of CDMA Unslotted ALOHA With Hybrid Type II ARQ Using Rate Compatible Punctured Turbo Codes

Yoon

Bar-Ness²

2004

“…Under the nonblocking assumption (infinite buffer size) and additive white Gaussian noise (AWGN) channel model, the throughput and average delay performance of RACH was investigated analytically with and without power ramping in [4]. The delay capture effect on performance was also studied.…”

Section: A Related Workmentioning

confidence: 99%

Analysis of power ramping schemes for UTRA-FDD random access channel

Yang

Yum

2005

The random access channel (RACH) in a universal terrestrial radio access-frequency division duplex (UTRA-FDD) system is a contention-based channel mainly used to carry control information from mobile stations (MS) to base stations (BS). The transmission of a random access request contains two steps: preamble transmission and message transmission. In preamble transmission, the power ramping technique is used to favor the delayed preambles by stepping up the transmission power after each unsuccessful access. In doing so, the success of transmitting a long-delayed preamble is increased due to the power capture effect. This paper analyzes the blocking, throughput, and delay performance of preamble transmission under three power ramping schemes with fixed, linear, and geometric step sizes. The interference caused by different power ramping schemes is also compared.Index Terms-Power ramping, random access channel (RACH), third-generation (3G) wireless communications, UTRA-FDD.

“…Thus, the pdf and cdf are given by [23] (15) (16) respectively, where . 3 For simplicity of presentation, an ideal chip sampling with no multipath interference is assumed. Note, however, that for small M N, the length of coherent accumulation, the multipath interference can be significant.…”

Section: A Statistics Of Variablesmentioning

confidence: 99%

Burst synchronization of slotted random access with preamble power ramping in the reverse link of cdma systems

Sheen

Tseng²,

2003

Efficient random access is one of the key designs in code-division multiple-access (CDMA) cellular systems. Random access is used by user equipment for initial access, requesting dedicated channels and transmitting short packet data to a base station. In random access, a preamble part is usually devised for fast and reliable burst synchronization, which is essential in order to avoid excessive access delay and/or repeated transmissions that may reduce the overall system capacity. This paper investigates the issue of burst synchronization for the slotted random access with preamble power ramping in the reverse link of CDMA systems. A flexible burst synchronizer based on a parallel-serial code-phase detector is proposed, which can be easily configured to achieve different complexity/performance tradeoffs. A general analysis is also presented with important design parameters being taken into account, including the number of correlators, power control error, power ramping step, diversity order, frequency offset, multipath combining, and others. The analysis is verified by computer simulations.Index Terms-Burst synchronization, power ramping, random access, wideband code-division multiple-access (WCDMA).