![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDT6HASV5jweIc1nKeyXMN6gJTlOys83kHaNK1SumRhThiOR8PUPtScMkZdNvQry9o3JoM74Nt9JVlpQqbi7jciTlN66MXBuA9Znpp36KrbHUZ19Rs6OddAzHre3rHhQwhLzELgfRplIo/s400/HSPAplus_Release8_RandS_3g4g.jpg)
Users should always be kept in the state that gives the best trade-off between data rate availability, latency, battery consumption and usage of network resources. As a complement to the data rate enhancements made to the dedicated state (CELL_DCH), 3GPP has also made significant enhancements to the common states (URA_PCH, CELL_PCH and CELL_FACH). Release 7 introduced HSDPA mechanisms in the common states in order to improve their data rates, latency and code usage. Release 8 introduces corresponding enhancements in the uplink, allowing base stations to configure and dynamically manage up to 32 common Enhanced Uplink resources in each cell.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgL__7njn4-JyQjpYtkxRDpMOs9_NkBW70ES6UoD5m0DLX799xxshoABaEyXBA1LXFbfBH_JZA7PhbeEXX4e6o5m78D_til7s59oYhYoLbLs-IDyt4r2B6snqB22_t5pJ1pTlFpabijXc/s400/Release7andRelease8_Huawei.jpg)
This enhancement improves latency and data rates for keep-alive messages (for example, from VPN or messenger applications) as well as web-browsing events, providing a seamless transition from EUL in common state to EUL in dedicated state.
As a further improvement of the CELL_FACH state, Release 8 introduces discontinuous reception (DRX), which significantly reduces battery consumption. DRX is now supported in all common and dedicated states.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhFTspRkZPnVLWRCcl1s0xGwfyaD8-0klqdX6opUrKfaWZNQ4gf32Hnm1nfC-9icvw2j8lzL7QnvPEb5mUURZmXE-hIvJ5nAhXPrjt4JQipzjDxmRk-MjMQp87lF_L1A_jE8TaJyYAOWW4/s400/EnhancedRACH_Release8.jpg)
Enhanced FACH and RACH bring a few performance benefits:
- RACH and FACH data rates can be increased beyond 1 Mbps. The end user could get immediate access to relatively high data rates without the latency of channel allocation.
- The state transition from Cell_FACH to Cell_DCH would be practically seamless. Once the network resources for the channel allocation are available, a seamless transition can take place to Cell_DCH since the physical channel is not changed.
- Unnecessary state transitions to Cell_DCH can be avoided when more data can be transmitted in Cell_FACH state. Many applications create some background traffic that is today carried on Cell_DCH. Therefore, Enhanced RACH and FACH can reduce the channel element consumption in NodeB.
- Discontinuous reception could be used in Cell_FACH to reduce the power consumption. The discontinuous reception can be implemented since Enhanced FACH uses short 2 ms TTI instead of 10 ms as in Release 99. The discontinuous reception in Cell_FACH state is introduced in 3GPP Release 8.
For more information see: LTE for UMTS: OFDMA and SC-FDMA Based Radio Access
1 comment:
in which spec series functionality is covered in more detail? 25.321/331
Post a Comment