This letter presents an early termination scheme for iterative multiuser detection in interleave division multiple access (IDMA) systems. Instead of handling an entire frame as a whole, each bit in the frame is separately considered. If further iterations are found to be dispensable in determining a bit, the estimate of the bit is immediately finalized, and all the calculations associated with the bit are bypassed afterward, diminishing the computational complexity. To confirm the dispensability, all log-likelihood ratios (LLRs) associated with a bit are examined. Once their magnitudes exceed a threshold, their statistical measures are unlikely to change even after a few more iterations, implying that further iterations are unnecessary. As a countermeasure for infrequent behaviors deviating from such an expectation, the signs of the LLRs in two consecutive iterations are compared. If they all match, the bitwise procedure is terminated. For the remaining bits not fulfilling the criterion, the procedure continues as usual. As a result, in the realm of practical signal-to-noise ratios, a significant number of iterations and operations can be discarded while sustaining the near-optimal error rate.

中文翻译：

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IDMA 系统多用户检测的按位提前终止

这封信提出了一种在交错分割多址 (IDMA) 系统中进行迭代多用户检测的早期终止方案。不是将整个帧作为一个整体来处理，而是单独考虑帧中的每一位。如果发现在确定比特时不需要进一步的迭代，则立即确定比特的估计，然后绕过与比特相关的所有计算，从而降低计算复杂度。为了确认可有可无性，检查了与比特相关的所有对数似然比 (LLR)。一旦它们的量级超过阈值，即使经过几次迭代，它们的统计度量也不太可能改变，这意味着不需要进一步的迭代。作为对偏离这种期望的罕见行为的对策，比较两次连续迭代中 LLR 的符号。如果它们都匹配，则按位过程终止。对于不满足标准的剩余位，程序照常继续。因此，在实际信噪比领域，可以丢弃大量迭代和操作，同时保持接近最佳的错误率。