TCP performance issues over wireless links

This article discusses the problems arising when the TCP/IP protocol suite is used to provide Internet connectivity over existing and emerging wireless links. Due to the strong drive toward wireless Internet access through mobile terminals, these problems must be carefully studied in order to build improved systems. We review wireless link characteristics using wireless LANs and cellular communications systems as examples. We then outline the performance problems of the TCP/IP protocol suite when employed over those links, such as degraded TCP performance due to mistaking wireless errors for congestion. We present various proposals for solving these problems and examine their benefits and limitations. Finally, we consider the future evolution of wireless systems and the challenges that emerging systems will impose on the Internet protocol suite     

Wireless Internet over LMDS: architecture and experimentalimplementation

LMDS is currently a promising emerging technology in broadband fixed wireless communications. The cellular structure, high data rates, and flexibility make it perfect for multimedia, digital television, and interactive services. These high-bandwidth multimedia services received most of the research attention until lately. There has been a clear gap when considering UDP/TCP/IP and other data services over LMDS. We examine the ramifications of using standard TCP/IP data communication over a two-layer LMDS system. We argue that the former emphasis only on multimedia and ATM-based communication over LMDS was a mistake. The most exciting prospect for LMDS should be in the role of enabling Internet and data services together with multimedia. We introduce a basic architecture for two-layer IP-LMDS based on a trial network built between 1996 and 2000     

Hop-by-hop toward future mobile broadband IP

We try to give some perspectives on likely trends in future wireless broadband networking. The treatment is an exploration of some technologies; due to the requirement to cover the topic from a broad perspective, it is not possible to go into technical details. We review current developments toward future mobile broadband networks, and then present the 4G paradigm of trying to combine heterogeneous networks, both cellular wireless hotspots and sensor networks, together with Internet protocols. We show how different networks play their own roles in the emerging infrastructure so that we can hop by hop wave the broadband network from mobile devices toward the fiber optic core network.     

Performance of dynamic spectrum access based on spectrum occupancy statistics

At present multiband wireless devices are able to select their working frequency only to a limited extent because of the strict, current spectrum regulation. Dynamic spectrum access is a promising approach that might solve this inefficiency. The authors focus on spectrum sensing, one of the main tasks involved. First, three strategies are compared to efficiently sense the current spectrum based on the spectrum occupancy information statistics. In contrast to the simulation-based studies, the authors evaluate the performance of those strategies on real spectrum occupancy data gathered during an extensive measurement campaign. The authors show that the usage of historical information considerably improves the spectrum sensing process and also that the modelling of the periodic behaviour of the licensed signals leads to negligible performance enhancements because only very few periods shorter than several minutes can be found within 20 MHz 6 GHz. Secondly, the authors unveil the fundamental tradeoff between the required bandwidth for the transmission and the total bandwidth that has to be sensed in order to guarantee that the required bandwidth is available. All the results are provided in terms of outage probability that can be viewed as an approximation of the packet loss rate.     

Optimizing Internet flows over IEEE 802.11b wireless local areanetworks: a performance-enhancing proxy based on forward errorcorrection

The success of the IP and its associated technologies has led to new challenges as we try to use it more widely in everyday communications. In particular, the drive toward wireless and highly heterogeneous infrastructures supporting IP services transparently and independent of the underlying physical layer is a challenge. In this context, this article focuses on introducing an implementation of a generic performance-enhancing proxy, called the wireless adaptation layer, and particularly its forward error control enhancement module. The error control module is a potentially important tool for achieving better UDP and TCP performance over the inherently unreliable wireless channels, and providing some adaptation for that. In order to assess the benefits and drawbacks of the selected design, we have also conducted some performance measurements over IEEE 802.11b WLANs     

Enhancing IP service provision over heterogeneous wirelessnetworks: a path toward 4G

Second-generation mobile radio systems have been deployed successfully worldwide and have evolved to higher data rates and services. Third-generation mobile radio systems are currently starting to be developed in different regions of the world. Today, the open question is how the third-generation systems will evolve. It is very likely that fourth-generation systems will not be a single standardized air interface, but a set of different technologies and standards. In particular, wireless LAN/wireless PAN type systems are designed for high/medium-data-rate access, low range, and, in general, low mobility. They are applicable to corporate networks and public access as a complement to cellular mobile radio systems for hot spot applications such as airports, hotels, and campuses. In this specific WLAN/WPAN framework and to guarantee an agreed QoS provision over such infrastructures, we propose a solution based on the wireless adaptation layer approach. In particular, aspects related to wireless link impairments and traffic requirements are approached by the implementation of configurable, modular software that is adapted to the specific conditions and needs of the particular wireless infrastructures     

Providing network connectivity for small appliances: a functionallyminimized embedded Web server

There is a strong trend toward embedding Internet capabilities into electronics and everyday appliances. We introduce the results from a research project where we have been working toward implementing a functionally minimized Web server on silicon. Although most embedded Internet appliances will use a microcontroller and software to enable TCP/IP and HTTP support, we argue that there are many applications where a hardware-based approach is more suitable. Our WebChip approach is a family of IPv6-compatible solutions toward the realization of embedded and minimized Web systems. The core parts of the implementation are a C-code library and VHDL code implementation. The solution is tested with an FPGA and can be later embedded into various ASIC chips. We argue that this approach is also commercially viable since the VHDL code can be delivered as an intellectual property block