A parallel 3GPP R8 project to LTE and SAE is the Evolved High Speed Packet Access, eHSPA, project (also referred to as HSPA+). The proposed eHSPA features represent a logical evolution from today’s HSDPA and HSUPA systems.
Roughly speaking, the eHSPA project focuses on three areas: • Optimising HSPA for real-time packet data services, like VoIP. A large part of achieving this goal relates to a more efficient use of the HSPA control channels.
• Increasing the system and user throughput. This is achieved by the introduction of higher order modulation (64QAM) and MIMO for HSPA. The theoretical maximum bit rate is around 40Mb/s for the DL and around 20Mb/s for the UL.
• Simplifying the network architecture. The eHSPA NodeB will take on parts of, or all of, the functionality of the RNC. In addition, the SGSN will be removed from the User Plane path (the so-called ‘one-tunnel solution’) allowing IP packets to be routed directly between eHSPA NodeB and GGSN. This can be seen in figure above, where ‘cSGSN’ is the SGSN Controller, and ‘xGGSN’ is the enhanced GGSN.
Evolved HSPA (HSPA+) in LTE
Evolved HSPA (High-Speed Packet Access) or HSPA+ is an enhancement of the previous HSPA technology, which aims to provide higher data rates and improved performance in mobile networks. Although LTE is a separate technology, HSPA+ remains an important part of the 3GPP evolution. Here’s how HSPA+ fits within the context of LTE:
- Higher Data Rates: HSPA+ provides faster data speeds than previous HSPA technologies. It can deliver peak download speeds of up to 168 Mbps and upload speeds of up to 22 Mbps under optimal conditions.
- Backward Compatibility: HSPA+ is designed to be backward compatible with earlier versions of 3G, making it easier for operators to deploy in areas where LTE has not yet been rolled out.
- Adaptive Modulation: HSPA+ uses adaptive modulation techniques to optimize data transmission based on the network conditions, increasing efficiency and throughput.
- Improved Spectral Efficiency: It improves spectral efficiency through techniques like MIMO (Multiple Input, Multiple Output) and higher-order modulation (64-QAM), allowing more data to be transmitted over a given frequency band.
- Coexistence with LTE: In many networks, HSPA+ and LTE coexist. HSPA+ continues to serve users in areas where LTE deployment is not available, ensuring seamless service for users with different devices or capabilities.
In summary, while LTE provides the highest speeds and performance for mobile broadband, HSPA+ remains an important upgrade to 3G networks, offering better data rates, improved efficiency, and backward compatibility with legacy devices. It ensures operators can meet user demand for high-speed data even as they transition to LTE.