Migration Process It is a two step process, – the first step involves the introduction of UMTS networks which involves a hardware change to the RAN network as new WCDMA air-interface is introduced. –the second step is a software upgrade to the RNC of WCDMA RAN.
Network Planning WCDMA technology has set new requirements to radio network planning All frequency dependent elements have to be updated and taken into account during planning (antennas, cables, power amplifiers, low noise amplifiers, filters, combiners…) WCDMA operates in the frequency band of 2100 MHz, which is much more higher than the 900 MHz and 1800 MHz typically in GSM All the WCDMA cells can use the same frequency -> reuse = 1 Interworking between WCDMA and GSM has to planned
Code and Frequency planning In WCDMA networks, cells are identified by: –Unique cell ID –Frequency –Scrambling code Scrambling code optimization is an important task in designing and deploying a WCDMA network. The total primary scrambling codes available in the WCDMA system is 512. Individual cells use channelization codes to separate users and communication channels: – All mobiles share the same frequency carrier. –Cells use orthogonal channelization codes to separate users and separate communication channels
Example Scrambling Code Optimization The following figure shows an example of scrambling code optimization. The cell scrambling code is the figure adjacent to the cell symbol. Each cell in this example is assigned a unique scrambling code.
HSDPA Basics Described in 3GPP Release 5 specifications – Enhances peak download data rate from current 384 kbps up to a theoretical maximum downloading peak rate of 14.4 Mbps (10,7 Mbps with ¾ coding rate) – Aimed for interactive and background services but streaming is also considered Requires investments to R99/R4 UMTS (WCDMA) network – Affects radio network HW and SW, core network SW, and transmission network HW – Can be deployed using small upgrades, not required for all BSs, RNCs – Does not require a completely new network structure – Protecting the current investments made to the network
In order to reduce Round Trip Time (RTT) new features have been implemented in BS, closer to the air interface Adaptive Modulation and Coding (AMC) – Depending on UE channel conditions (CQI) – QPSK, 16QAM – Coding rate (1/4 – 3/4) – Data rate adapted on 2 ms time basis Fast Retransmission – Hybrid Automatic Repeat reQuest (HARQ) – UE soft-combines data – Reduced RTT Fast Packet Scheduling (PS) – Scheduling of users on 2 ms time basis New radio channels included for HSDPA – DL: HS-(P)DSCH, HS-SCCH – UL: HS-DPCCH
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