Distributed Cooperative Relaying Based on Space-Time Block Code: System Description and Measurement Campaign

Abstract

In cooperative relaying, intermediate stations are required to enhance the end-to-end transmission performance. The performance of the cooperative relaying scheme has been investigated theoretically and via computer simulations. However, cooperative relaying using transmit diversity techniques in actual environments has not been investigated thus far. This paper presents an experimental system for distributed cooperative relaying using space-time block code and evaluations of its transmission performances in real propagation channels. To this end, four wireless stations-specifically, one source, two relays, and one destination-were developed using analog transceivers and field-programmable gate arrays for real-time digital signal processing. Sample timing and frequency synchronizations among the four wireless stations were established by using the received signals as a reference. The end-to-end error performance of distributed cooperative relaying was compared to those of noncooperative relaying schemes, and the performances of three relaying schemes were evaluated quasisimultaneously in terms of their cumulative distribution functions of the bit-error ratios (BERs). The experimental results indicated that the BER performance of the two-hop distributed cooperative relaying scheme was substantially superior to those of noncooperative two-hop relaying schemes, including a route diversity scheme.

A computationally efficient non-coherent technique for wireless relay networks

“…Space diversity using multi-antenna techniques has been introduced as an efficient way of counteracting the effects in wireless fading channels without the need for extra time or frequency slots as in conventional diversity techniques (time-and frequency-diversity) and without requiring additional power [1]- [6]. Recently, space-diversity techniques that use multiple-input multiple-output (MIMO) systems have been studied extensively [7]- [12].…”

“…Due to hardware limitations, multi-antenna techniques in ad-hoc networks may not always be feasible, especially with small device applications. As a solution, another form of space diversity is accomplished by exploiting the antennas of multiple terminals, called relays, to combat the fading due to the multi-path and shadowing propagation similar to MIMO systems [1], [20], [21]. Hence, this solution is usually dubbed "the relay channels".…”

“…Currently, many cooperative protocols have been suggested. These are divided into two main categories: the amplify and forward (AF) protocols [1], [13], [20] and the decode and forward (DF) protocols [7], [22]. Cooperative techniques can be categorized into two main classes regarding the availability of the channel state information (CSI).…”

“…Cooperative techniques can be categorized into two main classes regarding the availability of the channel state information (CSI). The first one is the coherent techniques [1], [22], where the channel information is estimated before performing these techniques. However, the complexity and cost of channel estimation grow with the number of transmit and receive antennas.…”

“…Moreover, DSTBC techniques can be used if the CSI changes too fast. Therefore, many DSTBC designs have been proposed recently [1], [20]- [27]. In the case of using two transmit antennas, the design of DSTBC is well established since there is a full rate complex orthogonal code.…”