Ongoing Development of 3G Networks

With the deployment and commercial application of HSPA networks worldwide, mobile broadband data services have become widely available on the global market. As a result, high-rate data services—especially video, music, and games—have begun to place greater demands on the mobile network (for higher rate, larger capacity, and better user experience). The commercialization of HSPA+ and LTE is therefore accelerating in response to this demand. Which strategy is best suited to HSPA+ and LTE evolution is an issue for 3G network planning and construction.

Technical Revolution Brought by HSPA+ and LTE

HSPA+ is the enhanced and evolved version of HSPA. In technical terms, the “+” indicates an improvement in modulation and antenna, among other things. As a fourth generation mobile technology, LTE is giving rise to greater technical innovation; however, enhancing network capacity and increasing download rate remains a priority for this new technology. On the one hand, HSPA+ and LTE are similar in their ability to enhance rate. On the other hand, their different modes create some differences. HSPA+ and LTE both improve mobile broadband bandwidth significantly—especially LTE, which is comparable to fixed network broadband.

Key techniques to enhance capacity and rate capability

Multiple-Input Multiple-Output (MIMO) is a key technique for HSPA+ and LTE. It uses multiple antennas at both the transmitter and receiver to block the fading channel. This enhances radio channel capacity and spectrum utilization, improves channel reliability, and reduces bit error ratio. Higher order modulation is another key technique. HSPA+ introduces 64QAM in the downlink (DL) and 16QAM in the uplink (UL). DL/UL peak rates in the cell can reach 21.6Mbps/11.5Mbps.

When both the 64QAM and MIMO are introduced in the DL, the peak rate can reach 43.2Mbps. LTE adopts OFDM modulation and supports flexible bandwidth configuration and spectrum allocation. When using 20MHz bandwidth and a 2×2 MIMO antenna scheme, LTE provides date rates of up to 150Mbps in the DL and 50Mbps in the UL.

In addition, Multi-Carrier HSPA (MC HSPA) allows dual-carrier or multi-carrier transmission in both the downlink and uplink. MC HSPA, when combined with 16QAM, 64QAM, MIMO and other techniques, yields peak rates of 23Mbps in the UL and 86Mbps in the DL.

Flat architecture and intelligent networks

In the LTE stage, the system undergoes some changes. First, the wireless system adopts eNodeB, which integrates the functions of the 3G RNC and NodeB, and significantly improves data processing efficiency. The LTE core network nodes are simplified as well, and a flat network architecture creates improved network performance.

Another innovation brought about by LTE is Self-Organizing Network (SON). Its four key functions: self-configuration, self-optimization, self-healing, and multi-operator management sharing, are specifically designed to reduce hands-on configuration and on-site maintenance, and to decrease O&M costs. 

How to Cope with the Coming Era of HSPA+ and LTE

IP transformation to cope with data growth

With the development of the HSPA market, introducing PC-based data services to mobile terminals has become central to the expansion of mobile broadband services.  Applications typically found in a fixed data network—such as advertising and searching services—have great profit potential in the mobile broadband market. These services require HSPA+ and LTE network, and should have extremely high data throughput.

First, in HSPA+ and LTE networks, RAN should be IP-based; that is, network elements such as RNC, NodeB, and eNodeB should be constructed on the all-IP hardware platform. These network elements should provide IP-based interfaces and support IP/ATM protocol stack in their software so that high-rate wireless data services can be carried by the all-IP network.

Second, IP-based transport is necessary. LTE is placing higher requirements on the end-to-end delay, so an IP-based transport network should have a flat architecture and higher QoS. Security also poses a great challenge for the IP network. Together, these place new requirements on the design and deployment of the transmission network.

Software upgrade to protect investment

It is true that with the tightening of competition, ARPU is diminishing. When operators construct 3G networks, they need to consider not only the current technology and service requirements but also how to protect the existing investment and reduce costs in future evolution. Software upgrade and sharing of hardware platforms are the first step in the evolution of a 3G network to HSPA+ and LTE. Therefore, during 3G network planning and equipment selection, future evolution strategies and support capabilities should be considered. A long-term plan should be implemented step by step in conjunction with network development.

Win-Win Strategy: HSPA→HSPA+→LTE

LTE is the network of choice for the future. However, because LTE does not support backward compatibility, operators have to outlay large amounts of money to purchase new frequency bands for the deployment of new networks. Moreover, the current LTE industry chain, which includes standard, chip, terminal, and the development of user habits, is not yet mature. 3GPP therefore initiates the development of HSPA+ (the upgraded version of HSPA) even after it has defined LTE as the target of evolution.

HSPA+ delivers functionality and performance similar to LTE, but it has far lower construction costs. There is no need for operators to buy new equipment or frequency bands when deploying HSPA+ in the existing HSPA network. Better network performance and capacity are achievable simply through software upgrade. Data services such as online multimedia (online music, reading, and streaming media) and mobile instant messaging (mobile newspapers and email) become available, allowing operators to maximize their profits. The high-rate data capability of HSPA+ also makes possible new IMS-based data services. With a greater variety of terminals coming into existence, users will surely find their favorite services. The initial development of user habits is important for the maturation of LTE, and helps limit operating risks.

LTE will be a primary technology and focus of market development in the future. But at present, and for several years to come, development from HSPA to HSPA+ and then to LTE will be most suitable. The core of this development lies in the initial deployment of HSPA+, and then LTE. Software must be updated first, then hardware; hotspots first, and then the network as a whole.

The deployment of LTE network should proceed as follows: First, deploy LTE on the new 2.6GHz frequency band, making it coexistent with existing 2G and 3G networks. Second, with the gradual migration of users to LTE, build a new LTE network on the original frequency bands of 2G/3G networks. This will form a dual-mode GSM/LTE, dual-mode UMTS/LTE or multi-mode GSM/UMTS/LTE networks. Finally, support multiple network modes via a single radio access network.

Nowadays global high-end operators have begun deploying HSPA+ and LTE networks. CSL, the biggest mobile operator in Hong Kong, launched the world’s first SDR-based HSPA+ network in March 2009. This all-IP network provides up to 21Mbps download speed and helps CSL deliver a variety of multi-media services including music download, video on demand, and interactive games. In September 2009, CSL announced the commencement of an LTE commercial trial network. It plans a smooth evolution to LTE through simple upgrade and modifications using the SDR base stations supplied by ZTE. 2G/3G/4G networks will be converged into one network.

Conclusion

In the long term, LTE and future wireless technologies will almost certainly replace current mobile networks. But this is a long process that leaves a wide opening for the development of UMTS networks. HSPA+ will play an important role by virtue of its own advantages. The new generation Uni-RAN solution, represented by ZTE SDR technology, allows multi-mode and multi-band networking. It takes into consideration both the operator’s investment and network evolution strategy, implements smooth network evolution by software upgrade and hardware sharing, enhances network performance and reliability, and helps create a win-win future for both operators and subscribers.