Towards Massive, Ultra-Reliable, and Low-Latency Wireless Communication with Short Packets
Towards Massive, Ultra-Reliable, and Low-Latency Wireless Communication with Short Packets
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发表时间：
2015-04
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通讯作者：
G. Durisi;T. Koch;P. Popovski
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作者：
G. Durisi;T. Koch;P. Popovski
高速无线系统设计的最新进展是基于信息理论原理，这些原理演示了如何有效传输长数据包。但是，即将到来的无线系统（尤其是5G系统）将需要支持使用短包的新型流量类型。例如，简短的数据包代表了传感器和机器对机器（M2M）通信的其他设备生成的最常见的流量形式。此外，有一些新兴的应用程序，其中预计小数据包应携带关键信息，这些信息应以低延迟和超高可靠性收到。当前的无线系统并非旨在支持短包传输。例如，当前系统的设计依赖于以下假设：与实际信息有效负载相比，元数据（控制信息）的大小可忽略不计。因此，使用启发式方法传输元数据不会影响整体系统性能。但是，当数据包短时，元数据的大小可能与有效载荷相同，并且传统的传输方法可能是高度最佳的。在本文中，我们回顾了信息理论的最新进展，该进步提供了控制短数据包传输的理论原则。然后，我们将这些原理应用于三个示例场景（双向通道，下行链路广播频道和上行链路随机访问频道），从而说明了在数据包短时如何优化控制信息的传输。这些示例带来的见解表明，设计支持短数据包的无线协议需要新的原则。这些原则将对系统设计产生直接影响。
Most of the recent advances in the design of high-speed wireless systems are based on information-theoretic principles that demonstrate how to efficiently transmit long data packets. However, the upcoming wireless systems, notably the 5G system, will need to support novel traffic types that use short packets. For example, short packets represent the most common form of traffic generated by sensors and other devices involved in Machine-to-Machine (M2M) communications. Furthermore, there are emerging applications in which small packets are expected to carry critical information that should be received with low latency and ultra-high reliability. Current wireless systems are not designed to support short-packet transmissions. For example, the design of current systems relies on the assumption that the metadata (control information) is of negligible size compared to the actual information payload. Hence, transmitting metadata using heuristic methods does not affect the overall system performance. However, when the packets are short, metadata may be of the same size as the payload, and the conventional methods to transmit it may be highly suboptimal. In this article, we review recent advances in information theory, which provide the theoretical principles that govern the transmission of short packets. We then apply these principles to three exemplary scenarios (the two-way channel, the downlink broadcast channel, and the uplink random access channel), thereby illustrating how the transmission of control information can be optimized when the packets are short. The insights brought by these examples suggest that new principles are needed for the design of wireless protocols supporting short packets. These principles will have a direct impact on the system design.