7.1 Technical Overview


IP in wireless networks plays different roles due to the varying capabilities and applications supported in these technologies. For example, personal area networks (PAN) are concerned with short-range communications within a home or a small office/home office (SOHO) environment for wireless connectivity and for applications like simple file and data transfer. Existing IP protocols with necessary adaptations to specific PAN radio technologies (e.g., Bluetooth, IEEE 802.15) can help achieve those goals.

WLAN, on the other hand, is meant for broadband wireless access in a larger environment, such as airports, hotels, universities, and malls. The intent of WLAN is similar to the Ethernet but provides a link-level wireless solution. Therefore, WLAN, just like Ethernet, can support IP on the network layer and various IP applications that are/have been developed based on the capabilities of the higher-layer protocols over IP.

Current cellular networks (2G and 3G) are some of the most complex network architectures ever deployed on a large scale and provide a complete solution for addressing, security, paging, mobility, accounting, and so on. They are strictly governed by standards developed in standards organizations like ETSI, 3GPP, and 3GPP2 for the purposes of vendor interoperability and transparency of the network services for users roaming to other networks. 2G cellular radios have limited bandwidth and costly radio resources. In 3G cellular, although the bandwidth is higher, the radio resources are still expensive. Cellular networks make use of strict radio admission control to allocate radio resources based on demand and availability. The IP suite of protocols is not well optimized for low-bandwidth and limited resource links.

Cellular networks provide idle mobility, also called roaming, and active call handoff functions to users without any noticeable glitch to allow for seamless mobility within an operator network and across different operator networks. All these features have been tried and tested and are currently in use on a large scale. Toward supporting similar mobility features, IETF is presently defining mobility solutions with IP (versions 4 and 6) that include idle mobility and handover. The IETF also formed a working group to handle internetwork roaming for authentication, authorization, and accounting (AAA) functions for large-scale deployments.

On the services level, cellular networks offer voice communications and an advanced set of call- related supplementary services that include features like call identity, forwarding, and restrictions. Recently introduced 3G cellular networks provide higher bandwidth in their packet core network and offer multimedia applications and Web services as a first step of service integration to the Internet. These IP applications are mainly data centric and work complementary to existing cellular voice services by making use of existing Internet infrastructure support and protocols. But they are not suitable to replace cellular functionality without due enhancements.

The first enhancements include support for real-time call establishments over IP networks leading to the development of an IP-based call/session control signaling (Session Initiation Protocol, SIP) to handle calls and other multimedia sessions. Support for real-time or priority-based traffic is not currently supported by the Internet, since IP treats all the packets the same. Without preferential treatment of packets, it is not possible to provide real-time communications as the service quality suffers significantly. This end-to-end preferential treatment of certain packets opened up a new set of problems: IP must manage, set up and guarantee these desired QoS features, such as delay, jitter, throughput, bit rate, and bit-error rate.

Cellular networks exclusively use the SS7 backbone in the core network to carry signaling. SS7 offers a robust and highly reliable network to carry signaling messages. Cellular networks have been designed to connect seamlessly to the PSTN, which provides landline telecommunication services. This enables mobile users to make calls to landline phones and vice versa. To remain connected to the PSTN network, IP networks must make use of gateways that will perform signaling and media interworking on the border of IP networks and PSTN. A lightweight, reliable transport protocol over IP is under development to be backward compatible with the SS7 protocol stack.

In order for IP to be applied ubiquitously to wireless networks, it must overcome the wireless challenges. The rest of this chapter discusses, at length, the individual challenges of IP applicability to wireless networks.



IP in Wireless Networks
IP in Wireless Networks
ISBN: 0130666483
EAN: 2147483647
Year: 2003
Pages: 164

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