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arXiv 0707.4656cs.ITmath.IT
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强异步通信

Communication under Strong Asynchronism

Aslan Tchamkerten, Venkat Chandar, Gregory Wornell

摘要:

我们考虑点到点离散无记忆通道上的异步通信。发射机在某一时刻开始发送一个块码字,该时刻均匀地分布在一定时间段内,这代表了复用水平。接收机必须通过顺序解码器来隔离消息,而不知道码字传输何时开始,但要知道识别级别A。我们感兴趣的是接收器能够多快地隔离发送的消息,特别是在A指数大于码字长度N的情况下,我们称之为“强分离”。这种稀疏通信模型可能代表了传感器在大部分时间保持空闲的情况,只是偶尔向需要快速采取行动的远程基站发送信息。第一个结果表明,可以保证消失的错误概率N趋于无穷大,而A增长为Exp(N*k),当且仅当k不超过“同步阈值”,一个常数,承认一个简单的封闭形式的表达式,并至少是一样大的同步信道的容量。第二个结果是一组可实现的严格正的速率在政权的特征,其中A是指数的N,和其中的速率是相对于预期的延迟之间的时间信息开始被发射,直到时间的接收器作出决定。作为第一个结果的应用程序,我们认为对映信号在高斯信道,并得出一个简单的必要条件之间的A,N,和SNR实现可靠的通信。

英文摘要:

We consider asynchronous communication over point-to-point discrete memoryless channels. The transmitter starts sending one block codeword at an instant that is uniformly distributed within a certain time period, which represents the level of asynchronism. The receiver, by means of a sequential decoder, must isolate the message without knowing when the codeword transmission starts but being cognizant of the asynchronism level A. We are interested in how quickly can the receiver isolate the sent message, particularly in the regime where A is exponentially larger than the codeword length N, which we refer to as `strong asynchronism.' This model of sparse communication may represent the situation of a sensor that remains idle most of the time and, only occasionally, transmits information to a remote base station which needs to quickly take action. The first result shows that vanishing error probability can be guaranteed as N tends to infinity while A grows as Exp(N*k) if and only if k does not exceed the `synchronization threshold,' a constant that admits a simple closed form expression, and is at least as large as the capacity of the synchronized channel. The second result is the characterization of a set of achievable strictly positive rates in the regime where A is exponential in N, and where the rate is defined with respect to the expected delay between the time information starts being emitted until the time the receiver makes a decision. As an application of the first result we consider antipodal signaling over a Gaussian channel and derive a simple necessary condition between A, N, and SNR for achieving reliable communication.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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