Thursday 10 March 2011

Dual Cell HSDPA

Dual-Cell HSDPA (also known as: Dual-Carrier HSPA or Dual-Cell HSPA) is a wireless broadband standard based on HSPA that is defined in 3GPP UMTS release 8.
Dual Cell (DC-)HSDPA is the natural evolution of HSPA by means of carrier aggregation in the downlink[1]. UMTS licenses are often issued as 10 or 15 MHz paired spectrum allocations. The basic idea of the multicarrier feature is to achieve better resource utilization and spectrum efficiency by means of joint resource allocation and load balancing across the downlink carriers.
An advanced HSPA network can theoretically support up to 28Mbit/s and 42Mbit/s with a single 5 MHz carrier for Rel7 (MIMO with 16QAM) and Rel8 (64-QAM + MIMO), in good channel condition with low correlation between transmit antennas. An alternative method to double the data rates is to double the bandwidth, i.e. 10 MHz by using DC-HSPDA. Additionally, some diversity and joint scheduling gains can also be expected [2] with improved QoS for end users in poor environment conditions where existing techniques such as MIMO spatial multiplexing cannot be used to increase data rates. In 3GPP a study item was completed in June 2008. The outcome can be found in a technical report [3]. New HSDPA UE categories 21-24 have been introduced that support DC-HSDPA. DC-HSDPA can support up to 42Mbit/s, but unlike HSPA, it does not need to rely on MIMO transmission.
From Release 9 onwards it will be possible to use DC-HSDPA in combination with MIMO used on both carrier[4]. The support of MIMO in combination with DC-HSDPA will allow operators deploying Release 7 MIMO to benefit from the DC-HSDPA functionality as defined in Release 8. While in Release 8 DC-HSPDA can only operate on adjacent carriers, Release 9 allow that the paired cells can operate on two different frequency bands.

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