Information theoretic secrecy for multiple access and broadcast channels

在当前的蜂窝系统中，运营商已经不仅提供语音通信等传统业务，而且还提供受一定保密约束的进一步的组播业务或保密业务。目前，多种业务的融合是通过在不同的逻辑信道上分配不同的业务并在物理层独立传输的策略来实现的。一般来说，这是相当低效的，因此，从信息论的观点来看，有一种趋势是有效地合并多个共存的服务，以便它们在相同的无线资源上工作。进一步的保密是通过应用密码技术在更高的层次上实现的。不幸的是，这些技术依赖于假设非合法接收者没有足够的计算能力来解码机密信息。然而，一般而言，这些指控很难得到证实。因此，研究诸如物理层保密技术之类的替代安全措施是有意义的，它们在物理层实现安全并且不依赖于这样的假设。因此，这种技术提供了所谓的无条件安全。本项目分析了多址和广播信道中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，我们想要分析如何实现信息理论安全，并描述其基本限制。在本项目中，我们进一步分析了发射端和接收端的信道知识对保密性的影响。特别是在具有外部窃听者的系统中，假设向非合法接收者提供信道的完美信道状态信息是非常不现实的。因此，我们需要稳健的战略，即使在渠道不确定的情况下也能实现安全。另一个研究课题是网络的拓扑。在某些网络中，发送器或接收器上有可用的辅助信息。我们想要分析边信息对安全的影响。

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.