In this work, Generalized Space-Time Super-Modulation (GSTSM) is introduced which enables the transmission of an additional flexible-rate and highly-reliable information stream concurrently with the conventionally transmitted symbols, without the need for increasing the corresponding packet length. This is attained by jointly exploiting the spatial and temporal dimensions of multiple-antenna systems, which enables efficient detection for conventional and additional information subchannels even in highly correlated channel conditions or AWGN channels. In the context of machine-type communications, GSTSM enables grant-free medium access without transmitting additional headers to convey each machine's signature information. Hence, it is shown that even at an extreme case where the data packets of two users are always colliding, GSTSM offers throughput gains of up to 33% compared to the best examined header-based scheme. For the same scenario, it is shown that GSTSM based on joint multi-user detection provides throughput gains of up to 2.5× compared with the case where users' signals are detected independently. In addition, it yields over 90% improvement in achievable rates compared with the schemes that require centralized medium-access coordination. For both joint and independent signal detection schemes, it is also shown that adopting an iterative detection/decoding approach allows to further improve the throughput gains.

中文翻译：

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广义时空超调制及其在无授权介质接入中的应用


在这项工作中，引入了通用空时超调制（GSTSM），它能够在传统传输符号的同时传输额外的灵活速率和高度可靠的信息流，而无需增加相应的数据包长度。这是通过联合利用多天线系统的空间和时间维度来实现的，即使在高度相关的信道条件或 AWGN 信道中，也能够有效检测传统和附加信息子信道。在机器类型通信的上下文中，GSTSM 可以实现无授权的介质访问，而无需传输额外的标头来传达每台机器的签名信息。因此，结果表明，即使在两个用户的数据包总是发生冲突的极端情况下，与经过最佳检验的基于标头的方案相比，GSTSM 也能提供高达 33% 的吞吐量增益。对于相同场景，结果表明，与独立检测用户信号的情况相比，基于联合多用户检测的GSTSM可提供高达2.5倍的吞吐量增益。此外，与需要集中式介质访问协调的方案相比，它的可实现速率提高了 90% 以上。对于联合和独立信号检测方案，还表明采用迭代检测/解码方法可以进一步提高吞吐量增益。