Design of Joint Source/Channel Codes for Rayleigh Fading Channels

瑞利衰落信道联合源/信道码设计

• 批准号: 9314221
• 负责人: Costas Georghiades
• 金额: $ 34.76万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-08-01 至 1999-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9314221&HistoricalAwards=false
• 关键词: Design; Joint; Source; Channel; Codes

9314221 Vaishampayan We address the issue of combined source and channel coding for fading channels. It is well-known that channel coding, together with interleaving, can be used to achieve an improvement n diversity order. However, these codes have traditionally offered uniform error protection for all bits transmitted. In reality, for many sources, some bits from the quantizer are more important than others. We show that unequal error protection schemes can offer greatly improved performance on the fading channel given a fixed diversity level in the system. We also provide a method for designing unequal error protection schemes in order to minimize a distortion criterion, subject to an overall system diversity level. Additionally, we note that the interleaving delay required in interleaved systems is very large compared to the diversity orders that the code provides. In speech coding applications the entire communications system must be designed to meet a delay budget. The interleaving delay thus restricts the delay that can be allocated to the source coder/decoder. We show that the construction of a channel code with a constraint on the interleaving delay can be treated as a problem of designing a code for a restricted number of independently slow fading channels in which interleaving is not allowed on any of the slow fading channels. The diversity order that the code can achieve is restricted to the number of independent channels available. However, the rate of the code is then restricted to the reciprocal of the diversity order. In order to get around this constraint, we use the fact that for continuous alphabet sources, not every transition probability for the effective channel as seen by the source coder/decoder need exhibit the maximum order of diversity. This allows the rate to the code to be increased. We will examine structured techniques for constructing combined source and channel codes for the Rayleigh fading channel. ***

9314221 Vaishampayan 我们解决了衰落信道的组合源和信道编码问题。 众所周知，信道编码与交织一起可以用来实现n分集阶数的改进。 然而，这些代码传统上为所有传输的位提供统一的错误保护。 实际上，对于许多源来说，量化器中的某些位比其他位更重要。 我们表明，在给定系统中固定分集水平的情况下，不平等的错误保护方案可以大大提高衰落信道的性能。 我们还提供了一种设计不等错误保护方案的方法，以便在总体系统多样性水平的前提下最小化失真标准。 此外，我们注意到，与代码提供的分集顺序相比，交织系统中所需的交织延迟非常大。 在语音编码应用中，整个通信系统的设计必须满足延迟预算。 因此，交织延迟限制了可以分配给源编码器/解码器的延迟。 我们表明，对交织延迟进行约束的信道代码的构造可以被视为为有限数量的独立慢衰落信道设计代码的问题，其中在任何慢衰落信道上不允许交织。 The diversity order that the code can achieve is restricted to the number of independent channels available. 然而，代码的速率则被限制为分集阶数的倒数。 为了解决这个约束，我们使用这样的事实：对于连续字母源，并非源编码器/解码器所看到的有效通道的每个转移概率都需要表现出最大阶的多样性。 这使得代码的速率得以提高。 我们将研究为瑞利衰落信道构建组合源代码和信道代码的结构化技术。 ***