Single-user performance of direct-sequence code-division multiple-access using relay diversity and power allocation

Abstract

In this contribution, the authors investigate the single-user-bound performance of a direct-sequence code-division multiple-access (DS-CDMA) system, where one source mobile terminal (MT) communicates with its base-station (BS) with the assistance of multiple relays. The authors assume that the communications channels experience both propagation pathloss and fast fading, and that the channels from the source MT to the BS and relays as well as that from the relays to the BS may experience different fast fading modelled correspondingly by Nakagami-m distributions. In the study, they assume both the single-user combining using maximal ratio combining and the multiuser combining, which are derived based on the maximum signal-tointerference-plus-noise ratio criterion. The bit-error-rate (BER) performance of the DS-CDMA is investigated associated with considering the locations of the relays as well as the power-allocation among the source MT and relays. From the study and simulation results, it can be shown that the achievable BER performance of the DS-CDMA depends on the locations of the relays and also on the power-allocation among the source MT and relays. When the relays of a source MT are chosen from a different area, the power-allocation should also be adjusted correspondingly in order to achieve the minimum BER. Furthermore, when optimum powerallocation is assumed, the BER performance of the DS-CDMA can be significantly improved, when increasing the number of relays assisting the source MT.

Non-Coherent Successive Relaying and Cooperation: Principles, Designs, and Applications

“…73 Laneman et al characterised both the decode-and-forward (DF) 74 and amplify-and-forward (AF) protocols in [11] and [12] by 75 evaluating both their diversity orders and their outage probabil- 76 ities. Similar concepts were investigated also by Sendonaris et 77 al. in [13] and [14].…”

Multiple-Symbol Differential Sphere Detection aided successive relaying in the cooperative DS-CDMA uplink

“…Provided that this condition was satisfied, the algorithm discussed in [12] provides a feasible method of extracting the different components from the resultant composite signal with an acceptable accuracy. Inspired by [12], the DS-CDMA technique was adopted in order to avoid the potential interference between the transmitted signals of the SN and RN, which was further developed for our successive relaying aided network. In more detail, first the…”

“…More explicitly, we are not constrained to the employment of decode-and-forward relaying schemes, when considering the interrelay interference cancellation problem in the context of cooperative systems. Hence the DS-CDMA despread, decode, re-encode and respread operations employed at the RN in [12] are avoided, therefore, the system's complexity is reduced. Additionally, the number of spreading sequences required is also lower compared to [12].…”

Power-Efficient Opportunistic Amplify-and-Forward Single-Relay Aided Multi-User SC-FDMA Uplink

“…This allows us to jointly exploity the benefits of both time-and frequency-diversity for the sake of mitigating the deleterious effects of wireless propagation and/or for increasing the attainable system throughput [2], [3]. Recently, the family of cooperative diversity oriented Multiple-Access (MA) techniques has been invoked in order to design the uplink of advanced cooperative cellular networks [4]- [6]. Furthermore, the cooperative concepts have been extended to broadband systems by designing techniques for mitigating the effects of frequency-selective fading with the aid of Multi-Carrier (MC) techniques associated with appropriate source/relay power sharing [7], [8].…”