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We present a new space-time encoder based on packet-level redundancy which can increase the space-time encoder rate beyond unity without compromising diversity gains. A complementary low-complexity decoding algorithm based on maximum ratio combining and successive interference cancelation is further proposed. A major merit of the decoding algorithm is that it allows to adaptively tradeoff between diversity and multiplexing gains based on the estimated channel parameters at the receiver without requiring any channel state information at the transmitter. System level simulation results give insight into the advantages of the proposed scheme when compared to its Alamouti and MIMO multiplexing based on single value decomposition counterparts.

The usage of multiple antennas has proven to be a good remedy to the unreliability of the wireless channel as it offers significant diversity and/or multiplexing gains relative to single antenna systems. In particular, space-time coding (STC) [

In this work, we present a new way of generating space-time codes which is based on combining two (or more) data symbols into one, in a way similar to network coding [

The rest of this paper is organized as follows. Section

We propose a space time block encoder where at least one of the transmit instances uses a finite field encoding operation between at least two data elements. For instance, a bit wise modulo-2 operation may be applied to the bits of different data streams. As the bits from two (or more) streams are combined together into one resultant stream, the space-time encoder rate can be considerably increased without compromising the desired redundancy. The resultant data streams are then mapped to the physical transmitting antennas.

In this work, we limit our study to the case of a

At the output of the encoder, the following coded matrix is assumed:

A

In the following we will derive the signal-to-interference-and-noise-ratio (SINR) equations based on MRC and SIC at the receiver.(Alternatively, Minimum Mean Square Error (MMSE) or Maximum Likelihood (ML) decoding may as well be used.) The transmission protocol consists of two transmission slots,

The predecoding SINR is the SINR computed based on the signals received after transmissions during the times

Flowchart of the proposed decoding algorithm.

The baseband received symbol at the

Depending on the received signal strength, we can distinguish between two cases.

In the first case, the received power from the first transmit antenna is stronger than the received power from the second transmit antenna. In that case

In the second case, the received power from the second transmit antenna is stronger than the received power from the first transmit antenna. Here

Following the SINR evaluation of the transmitted coded symbols (i.e., predecoding SINR), the modulated symbols will be estimated by the space-time decoder. Figure

We distinguish between two main decoding scenarios that offer different diversity-multiplexing tradeoffs.

In the first scenario, the direct links are the strongest and both

In the second scenario, one of the symbols

In this case, the symbol

In this case, the symbol

The equivalent SINRs of the different transmitted symbols will then be given by

Using the postdecoding SINRs derived in the previous subsection, the sum-capacity for all the different scenarios can be written as follows:

A network deployment with seven cells is considered in order to measure the performance in the presence of inter-cell interference. Each cell has a radius of

As the main goal of this work is to evaluate the capacity performance of the proposed scheme, we opt to use system-level simulation. The evaluation of the error performance, hence the usage of link-level simulation, is left as a future work. However, the SINR results that were included should give a hint about the robustness of each simulated scheme.

The proposed scheme is evaluated and compared to the

Normalized capacity of the evaluated schemes.

SINR performance of the evaluated schemes.

In this work, we suggested the imitation of simple linear network coding at transmitters possessing multiple antennas, and we showed how this could be exploited in order to design redundant high-rate space-time codes. We proposed a complementary low-complexity decoding algorithm based on successive interference cancelation that can adaptively tradeoff between diversity and multiplexing gains without requiring any channel state information at the transmitting side. System level simulation results were presented as a proof of concept and to gain insight into the advantages of the proposed scheme.