Mutual information based rate adaptation for MIMO-OFDM systems with finite signal alphabets
Mutual information based rate adaptation for MIMO-OFDM systems with finite signal alphabets
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DOI：
10.1109/wsa.2008.4475538
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发表时间：
2008-02
期刊：
影响因子：
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通讯作者：
C. Bockelmann;D. Wübben;K. Kammeyer
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文献类型：
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作者：
C. Bockelmann;D. Wübben;K. Kammeyer
我们考虑了一个应用了空间复用的单用户MIMO-ofdm系统，并制定了速率分配算法以在每个子载波的基础上调整所使用的调制字母表。作为考虑包括关于比特或帧错误率(BER，FER)的信道码的系统行为的手段，针对几个M-QAM字母表研究了ofdm符号的归一化平均互信息(Nami)。为此，推导了具有M-QAM信号字母表的MIMO系统的互信息的近似，并将其与信道分解方法进行比较，以找到复杂度和精度之间的折衷。在互信息结果的基础上，介绍了两种利用该信道知识的算法。一方面，可以在假设固定速率要求的情况下优化误码率，另一方面，可以在BER/FER约束下优化所获得的传输速率。在这两种情况下，使用从特定信道码的模拟系统行为导出的NAMI阈值来通过贪婪算法调整所分配的调制字母表，以在误差容限内实现目标NAMI。
We consider a single user MIMO-OFDM system where spatial multiplexing is applied and formulate rate allocation algorithms to adapt the used modulation alphabet on a per subcarrier basis. As a means to consider the system behavior including the channel code regarding bit or frame error rate (BER, FER) versus normalized average mutual information (NAMI) of an OFDM symbol for several M-QAM alphabets is investigated. To this end an approximation to the mutual information of MIMO systems with M-QAM signal alphabets is derived and compared to channel decomposition approaches to find a complexity/accuracy trade-off. Based on the mutual information results two algorithms using this channel knowledge are introduced. On the one hand, the error rates can be optimized assuming a fixed rate requirement and on the other hand the achieved transmission rate can be optimized under a BER/FER constraint. In both cases a NAMI threshold derived from the simulated system behavior for a specific channel code is used to adapt the allocated modulation alphabets via a greedy algorithm to achieve the target NAMI within an error margin.