Packet data messaging over TETRA: network performance analysis

In this paper, we address various aspects of packet data transmission in terrestrial trunked radio (TETRA) networks giving particular emphasis on the performance of applications transmitting small messages between a number of radio terminals and a fixed server. The utilization of such applications is constantly increasing in public safety networks and so does the need to dimension and configure TETRA networks to meet their reliability, delay and loss requirements. We present simulation results for a variety of practical scenarios such as loading the packet data channel (PDCH) with different mobile station (MS) populations engaged in transmitting packet data (PD) at various rates. We quantify key performance indicators of the PDCH such as packet delay and packet loss rate. Furthermore, we provide an in-depth analysis of the impact of non-PD MS population—i.e., the loading of main control channel (MCCH)—on the average packet delay. Our results provide an insight of how network loading parameters interact with the protocol performance and may help in dimensioning and planning TETRA networks, and in particular, in determining the number of PD terminals that can be supported in a cell for a given traffic profile and QoS requirements.     

下一代3GPP系统话音呼叫切换机制（上）

演进的3GPP（第三代合作伙伴计划）系统是支持若干无线电接入技术和若干移动机制的混合移动网络结构。本文简要回顾该系统的结构及其关键组成,重点强调若干部署情形中支持话音呼叫移动性的方法。首先介绍称之为单模无线电话音呼叫连续性的机制,该机制能使从E-UTRAN（演进的通用移动电信系统陆地无线接入网）接入到遗留的UTRAN/GERAN（通用移动电信系统陆地无线接入网/增强数据率的全球移动通信系统演进无线接入网）或1xRTT的VoIP呼叫进行中间呼叫切换。然后着重描述不支持E-UTRAN上话音服务的部署情形,并介绍称为回落原地的机制,该机制能在话音呼叫的开始从E-UTRAN到UTRAN/GERAN或1xRTT进行切换。最后介绍由IP多媒体子系统实现的应用层话音呼叫切换机制。本文的结论是,下一代3GPP系统是高度完善的移动通信系统,它支持广泛的话音呼叫移动性机制,并能满足所有的商业部署需要。     

A study of CDPD forward channel performance with coherent and differential detection

The media access control (MAC)-layer performance of the cellular digital packet data (CDPD) forward channel is studied and a new technique to improve the performance is proposed. The study is based on a computer simulation model wherein a CDPD base station continuously transmits a sequence of packets to a CDPD mobile station. We consider a Rayleigh fading channel and demonstrate how the performance metrics are affected by the channel characteristics. At the reception stage, we consider both coherent and differential reception. We argue that the throughput at the MAC layer is affected not only by the error performance of the physical layer, but also by several design characteristics of the MAC layer, including the block length and the alignment between blocks and packets. We illustrate the block error rate, packet error rate, and throughput performance by simulation results, and we show how the receiver may discard data, which is correctly received but nevertheless useless. Our main conclusion is that the CDPD forward-channel performance could be significantly improved should the identified deficiencies are eliminated. For this purpose, we propose a new automatic repeat request (ARQ) protocol that operates in the MAC layer to correct the erroneous blocks by means of retransmissions, and we study its performance. In addition, we discuss an adaptive scheme that maximizes the forward-channel performance by automatically enabling and disabling the ARQ protocol according to the channel conditions.     

Editorial

Mobile Networks and Applications -     

Media-independent handover for seamless service provision in heterogeneous networks

The performance of current Internet applications is based mainly on the capabilities of the underlying network technologies. Modern access systems usually can satisfy delay, loss, or bandwidth requirements; however, design inconsistencies can lead to service degradation as the terminals move across different systems. In this article, the focal point is the satisfaction of service requirements during mobility and more specifically, how the emerging IEEE 802.21 standard enables seamless, inter-technology handover. Based on prior work and a well-known example of seamless mobility, the main seamless mobility principles are identified and used as the basis for further evaluating the potential of the IEEE 802.21 standard to meet the requirements of applications for minimum disruption during an inter-technology handover.     

Packet data over cellular networks: the CDPD approach

Cellular digital packet data is a mobile packet data technology that operates on the spectrum assigned to a telephone cellular network, such as the Advanced Mobile Phone Service. This article undertakes a thorough survey of the CDPD radio interface and explores the main functional layers of this interface. Specifically, it extensively studies the physical layer, the data link layer, and the subnetwork-dependent convergence protocol, and explains their semantics and functional characteristics. Furthermore, it emphasizes several significant aspects such as the medium access procedure, the forward and reverse channel configurations, the data multiplexing scheme, and the channel hopping procedure     

Interworking techniques and architectures for WLAN/3G integration toward 4G mobile data networks

The intense wireless LAN standardization and R&D activities worldwide, combines with the recent successful deployment of WLANs, provide prime evidence that WLAN technology will play a key role in the fourth generation of mobile data networks. In this context, there is a strong need to integrate WLANs with 3G mobile data networks and develop hybrid mobile data networks capable of ubiquitous data services and very high data rates in strategic locations. This article addresses this need by proposing and discussing some novel architectures able to provide internetworking between WLAN and 3G networks, and meet the requirements of the most common internetworking scenarios. These architectures can enable 3G subscribers to benefit from high-throughput IP connectivity in hotspots and also to attain service roaming across several radio access technologies, such as IEEE 802.11, HiperLan/2, ULTRAN, and GERAN.