Concurrent transmission (CT) has been widely adopted to optimize the throughput of various data transmissions in wireless networks, such as bulk data dissemination and high-rate data collection. In CT, besides the possible data frame collision at receivers, we observe that acknowledgment frame (ACK) collision at senders can also significantly diminish concurrency opportunities. In this article, to avoid the potential ACK collision in CT, we propose ALIGNER which develops a new transmission pattern to coordinate concurrent senders in a distributed manner. The key idea is to align the silent periods of concurrent transmitters. To achieve this goal, we align the end of data frames concurrently transmitted by several senders. Therefore, the potentially arriving ACKs can avoid a collision with ongoing data transmissions because the concurrent senders are in a listening state to wait for receivers’ ACKs for a short and fixed period. ALIGNER can be applied for both deterministic and opportunistic forwarding protocols. It optionally uses a random back-off and slotted ACK mechanism to avoid a potential collision among simultaneously arrived ACKs in opportunistic forwarding. In addition, ALIGNER adopts a tailor-made metrics to analyze the throughput benefit of concurrent transmission for both deterministic and opportunistic data collection protocols. We have implemented ALIGNER in TinyOS and conducted extensive experiments on a real testbed. Experimental results show that ALIGNER can significantly increase the concurrency opportunities in both deterministic (up to 105%) and opportunistic (up to 89.7%) forwarding compared with the state-of-the-art CT methods.

中文翻译：

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突破低功耗无线网络传输并发的极限

并发传输（CT）已被广泛用于优化无线网络中各种数据传输的吞吐量，例如批量数据传播和高速数据采集。在 CT 中，除了接收者可能发生的数据帧冲突外，我们观察到发送者的确认帧 (ACK) 冲突也会显着减少并发机会。在本文中，为了避免 CT 中潜在的 ACK 冲突，我们提出了 ALIGNER，它开发了一种新的传输模式来以分布式方式协调并发发送者。关键思想是对齐并发发射器的静默期。为了实现这个目标，我们对齐多个发送者同时传输的数据帧的结尾。所以，潜在到达的 ACK 可以避免与正在进行的数据传输发生冲突，因为并发发送者处于侦听状态以在短且固定的时间段内等待接收者的 ACK。ALIGNER 可以应用于确定性和机会性转发协议。它可选地使用随机退避和时隙 ACK 机制来避免机会转发中同时到达的 ACK 之间的潜在冲突。此外，ALIGNER 采用量身定制的指标来分析确定性和机会性数据收集协议的并发传输的吞吐量优势。我们已经在 TinyOS 中实现了 ALIGNER，并在真实的测试平台上进行了广泛的实验。