HSDPA (High-speed Downlink Packet Access):

HSDPA is a high-speed downlink data service that can be deployed on the existing 3G network infrastructure. The operators can deploy the first phase on the existing UMTS R99 network, using the same UMTS CH (as shown in Figure 2.39) and use the power headroom not utilized by the UMTS traffic.

This provides the mobile operator with a deployment strategy that can support the need for high-speed downlink data rates, at a relative low deployment cost. Many operators will prefer to use a separate CH for HSDPA, because loading the existing UMTS R99 carrier with HSDPA will cause the network to run constantly on a higher load rate, increasing the noise on the existing UMTS CH, degrading the UMTS capacity.

Why will the operators prefer to use HSDPA?

• Typically the highest data load is on the downlink.
• HSDPA will have a trunking gain of the radio capacity.
• There is no need for distributed APs like with Wi-Fi.
• Operators can use their existing UMTS network to launch HSDPA.
• HSDPA is more spectrum-efficient compared with EDGE and UMTS.
• There is higher spectrum efficiency, more data per MHz.
• There are fewer production costs per Mb.
• There are higher data speeds, up to 14 Mbps, with indoor DAS systems.
• Mobile operators can compete with Wi-Fi using HSPA.

HSDPA Key Features:

• Downlink data Rates up to 14.4 Mbps.
• No soft handover, so pico cells overlapping in the same building will produce ‘self interference’
• Can use the same channel as UMTS by utilizing the ‘power headroom’ for HSDPA
• Typical operators will launch HSDPA on a separate carrier, to minimize noise increase on the UMTS service.
• HSDPA is a downlink data service; users will use UMTS on the uplink until HSUPA is deployed.
• For the uplink data transmission from the mobile, UMTS R99 is used until HSUPA is launched in 2008 to cater for higher uplink data rates.