Future trends
Wideband CDMA (WCDMA)
By the year 2000, there could be 600 million mobile phones users around the world. In the future the demand the demand on wireless access will grow. Users will want to use wireless access not only for voice communications, but also for applications such as accessing the corporate LAN, using the Internet or instruments, videoconferencing and sending and retrieving high quality pictures.
Before this can happen, the capabilities of wireless networks-in terms of bandwidth-must be improved. This is what WCDMA is all about. The third generation can reach high bit rates up to 2Mbps,featuring a higher capabilities.
a. Technical Highlights
The WCDMA system will provide instant wireless access to multimedia services at bit rates up to 2 Mbps, yet it will also carry voice traffic coast-effectively.
WCDMA wireless access can be added to an existing digital wireless network such as GSM, allowing a sensible migration off for existing network operators.
Radio infrastructure coasts are kept low with CDMA, because existing GSM sites and equipment can be reused.
Also fading is reduced, as a result of the improved frequency diversity effects of the wider 5 MHz channel bandwidth.
b. The Third Generation Goals
· High voice quality comparable to wireline service.
· High security comparable to the fixed telecom network.
· A Data rate up to 2 Mbps for local or indoor/slow-moving access, and 384 Kbps for wide area access.
· Support for several simultaneous connections .( a user can browse the internet and at the same time making a phone call to a different destination)
· National and International roaming.
· Capable of handling packet and circuit - switched services, including Internet (IP) and videoconferencing.
· High spectral efficiency to make maximum use of limited bandwidth.
c. Key Features of WCDMA
· Service Flexibility: WCDMA allows each 5 MHz carrier to handle mixed services ranging from 8Kbps up to 2 Mbps. Also Circuit and packet-switched services can be combined on the same channel allowing true multimedia services with multiple packet or circuit connections on a single terminal.
· Spectrum Efficiency: WCDMA makes very efficient use of the available radio spectrum .No frequency planning is needed, since one cell reuse is applied.
· Capacity and Coverage: WCDMA radio frequency transceivers can handle eight times more voice users than narrowband transceivers. Each RF carrier can handle 100 simultaneous voice calls, or 50 simultaneous Internet type data users per RF carrier. While the capacity of WCDMA is approximately double that of the narrowband CDMA in urban and suburban environments.
· Superior voice capacity: Although the primary purpose of WCDMA is to carry high bit rate multimedia traffic, it is also a very spectrum efficient mechanism for voice traffic. An operator with 2 x 15 MHz spectrum allocation will be able to handle at least 192 voice calls per cell sector. This compares with around 100 voice calls per cell sector in a GSM network.
· Fast service access: To support instant access to multimedia services, a new random access procedure has been developed, using fast synchronization to handle 384 Kbps packet-data services. This requires only a few tenths of a millisecond to set up connections between a mobile user and a base cell.
· Terminal economy/simplicity: The signal processing required in WCDMA handsets is low compares with alternative technologies. Less complex, Therefore lower cost terminals will be easily mass-produced, leading to greater economies of scale, more competition, and greater choice for network operators and end users.
· Migration from GSM: WCDMA uses a similar network protocol structure (signaling) as GSM, and therefore will be able to use existing GSM network as the core network infrastructure. WCDMA therefore provides an opportunity for global deployment , and offers all these existing GSM operators the chance to build third-generation wireless access on their existing structures.
