Information theoretic secrecy for multiple access and broadcast channels

在目前的蜂窝系统中，运营商不仅提供传统的服务，如语音通信，而且还提供进一步的多播服务或保密服务，这些服务受到一定的保密约束。目前，多业务的集成是通过在不同的通道上分配不同的业务，在物理层独立传输的策略来实现的。一般来说，这是非常低效的，因此从信息论的角度来看，有一种趋势是有效地合并多个共存的服务，使它们在相同的无线资源上工作。通过应用加密技术在更高层次上实现进一步的保密。不幸的是，这种技术依赖于非合法接收者解码机密信息的计算能力不足的假设。然而，一般来说，这些假设很难得到证实。因此，研究替代安全措施（如物理层保密技术）是有意义的，它在物理层实现安全，而不依赖于这些假设。因此，这些技术提供了所谓的无条件安全性。该项目分析了多址和广播信道的信息理论或物理层安全。这些是蜂窝系统中上行链路和下行链路的基本模型，因此对移动通信很重要。在这个项目中，我们想分析如何实现信息理论上的安全，并描述基本的限制。在本项目中，我们进一步分析了发送端和接收端的信道知识对保密性的影响。特别是在带有外部信号发射器的系统中，假设信道状态信息完美地传递给非合法接收方是不现实的。因此，我们需要健壮的策略，即使在通道不确定的情况下也能实现安全。另一个研究课题是网络拓扑。在某些网络中，在发射机或接收机上有可用的侧信息。我们要分析侧面信息对安全性的影响。

In current cellular systems, operators already offer not only traditional services such as voice communication,but also further multicast services or confidential services that are subject to certain secrecy constraints.Nowadays, the integration of multiple services is realized by policies that allocate different services on differentlogical channels and transmit them independently at the physical layer. In general this is quite inefficient andthus there is a trend to merge multiple coexisting services efficiently from an information theoretic point of viewso that they work on the same wireless resources. Further secrecy is realized on higher levels by applyingcryptographic techniques. Unfortunately, such techniques rely on the assumption of insufficient computationalcapabilities of non-legitimate receivers for the decoding of the confidential information. In general, however, those asumptions are difficult to verify. Thus, it is of interest to investigate alternative security measures such as physical layer secrecy techniques, which realize security at the physical layerand do not rely on such assumptions. Therefore, such techniques provide so-called unconditional security.This project analyzes information theoretic or physical layer security in multiple access and broadcastchannels. These are the basic models for the uplink and downlink in a cellular system and, thus, important formobile communication. In this project we want to analyze how to achieve information theoretic security and tocharacterize the fundamental limits. In this project we further want to analyze the impactof channel knowledge at the transmitter and receiver on the secrecy. Especially in systems with an externaleavesdropper, the assumption of perfect channel state information of the channel to the non-legitimatereceiver is quite unrealistic. Therefore, we need robust strategies that achieve security even under channeluncertainty. Another research topic is the topology of the network. In certain networks there is side informationavailable at the transmitter or receiver. We want to analyze the impact of side information on the security.