Tuesday, December 09, 2008
HSDPA-High-Speed Down link Packet Access
High-Speed Down link Packet Access (HSDPA) is a 3G (third generation) mobile telephony communications protocol in the High-Speed Packet Access (HSPA) family, which allows networks based on Universal Mobile Telecommunications System (UMTS) to have higher data transfer speeds and capacity. Current HSDPA deployments support down-link speeds of 1.8, 3.6, 7.2 and 14.4 Mbit/s. Further speed increases are available with HSPA+, which provides speeds of up to 42 Mbit/s downlink.
The amount of the channelization code tree, and thus network bandwidth, allocated to HSDPA users is determined by the network. The allocation is "semi-static" in that it can be modified while the network is operating, but not on a frame-by-frame basis. This allocation represents a trade-off between bandwidth allocated for HSDPA users, versus that for voice and non-HSDPA data users. The allocation is in units of channelization codes for Spreading Factor 16, of which 16 exist and up to 15 can be allocated to HSDPA. When the base station decides which users will receive data on the next frame, it also decides which channelization codes will be used for each user.
This information is sent to the user devices over one or more HSDPA "scheduling channels"; these channels are not part of the HSDPA allocation previously mentioned, but are allocated separately. Thus, for a given 2 ms frame, data may be sent to a number of users simultaneously, using different channelization codes. The maximum number of users to receive data on a given 2 ms frame is determined by the number of allocated channelization codes.
The amount of the channelization code tree, and thus network bandwidth, allocated to HSDPA users is determined by the network. The allocation is "semi-static" in that it can be modified while the network is operating, but not on a frame-by-frame basis. This allocation represents a trade-off between bandwidth allocated for HSDPA users, versus that for voice and non-HSDPA data users. The allocation is in units of channelization codes for Spreading Factor 16, of which 16 exist and up to 15 can be allocated to HSDPA. When the base station decides which users will receive data on the next frame, it also decides which channelization codes will be used for each user.
This information is sent to the user devices over one or more HSDPA "scheduling channels"; these channels are not part of the HSDPA allocation previously mentioned, but are allocated separately. Thus, for a given 2 ms frame, data may be sent to a number of users simultaneously, using different channelization codes. The maximum number of users to receive data on a given 2 ms frame is determined by the number of allocated channelization codes.
# posted by margh @ 3:05 PM 
