Abstract
Distributed space–time block coding is a diversity technique to mitigate the effects of fading in multi-hop wireless networks, where multiple relay stages are used by a source to communicate with its destination. This article proposes a new distributed space–time block code called the cascaded orthogonal space–time block code (COSTBC) for the case where the source and destination are equipped with multiple antennas and each relay stage has one or more multiple antenna relays. Each relay stage is assumed to have receive channel state information (CSI) for all the channels from the source and all relays from previous stages to itself, while the destination is assumed to have receive CSI for all the channels. To construct the COSTBC, multiple orthogonal space–time block codes (OSTBCs) are used in cascade by the source and each relay stages. In the COSTBC, each relay stage separates the constellation symbols of the OSTBC sent by the preceding relay stage using its CSI, and then transmits another OSTBC to the next relay stage. COSTBCs are shown to achieve the maximum diversity gain in a multi-hop wireless network with linear decoding complexity thanks to the connection to OSTBCs. Several explicit constructions of COSTBCs are also provided, and their performance is simulated in different relay configurations.
Highlights
Distributed space–time block coding (DSTBC) is a technique to improve reliability in relay-assisted communication, where one or more relays help the source to communicate with its destination
We show that cascaded orthogonal space–time block code (COSTBC) achieve the maximum diversity gain in a multi-hop wireless network when each symbol of the code is decoded independently, resulting in linear decoding complexity similar to single symbol decodable codes
Even though COSTBCs are not single symbol decodable, we show that with COSTBCs, maximum diversity gain can be achieved if the destination decodes all constituent symbols of COSTBCs independently of each other according to rule (10)
Summary
Distributed space–time block coding (DSTBC) is a technique to improve reliability in relay-assisted communication, where one or more relays help the source to communicate with its destination. We design maximum diversity gain achieving DSTBCs with low-decoding complexity for a multi-hop wireless network where the source, the destination, and the relay nodes are equipped with multiple antennas. We prove that for a two-hop network and when the destination has a single antenna, by adding channel coefficient-dependent noise terms to the received signals, COSTBCs have the single symbol decodable property for any number of source and relay antennas. Exploiting the orthogonality property of the OSTBCs transmitted by each relay stage, the received signal at the destination can be separated in terms of individual symbols transmitted by the source as follows. COSTBCs are single symbol decodable STBCs after adding some channel coefficient-dependent noise terms to the received signals for N = 2 and M2 = 1.
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