Nowadays most of mobile operators around the world operate both UMTS and LTE networks. UMTS services are still growing in many countries and will continue to be a main source of revenue streams for operators over the next few years. But in the meanwhile LTE services are growing rapidly, and mobile networks need to evolve from existing 2×2 MIMO to 4×4 MIMO to meet the explosive growth of data traffic. The evolution will be a long-term process for most operators.
There are three major challenges operators have to face when they evolve their networks from UMTS/LTE to higher-order MIMO LTE.
- Enhance both UMTS and LTE network capacity.
- Get ready for 4×4 MIMO LTE evolution timely and effectively.
- Protect the existing network investment.
Several solutions are available in the industry for MIMO evolution. These solutions can improve network capacity but do not have enough flexibility in network evolution or are even difficult to protect existing network investment.
These solutions cannot reuse the widely available four-port antennas. Although multi-port antennas such as six-port or eight-port antennas provide more ports, they still have a limited number of ports available for low bands such as 1.8GHz and 2.1GHz. Operators often need to use external combiners for multi-band site deployment. This complicates installation and maintenance and thus increases costs.
Horizontal six-sector split is a common solution for UMTS capacity enhancement, but it has distinct disadvantages. This solution requires new network planning, takes long time to deploy, and may waste the investment in existing six-sector antennas when three-sector LTE antennas will be used in future.
Therefore operators expect a complete solution that can address all these issues. The solution should not only enhance network capacity but also be easy to deploy, save costs and protect investment. X-Site is such a complete and effective solution put forward by ZTE.
Features and Benefits
The X-Site solution consists of three parts: RRU cascading, vertical sector split, and X antenna.
- RRU Cascading
RRU cascading is a technology that uses internal combiners and supports cascading of multiple RRUs on different frequency bands (Fig. 1). X-Site RRU cascading enables service provision on multiple bands without changing existing two-port or four-port antennas. This saves costs in external combiners and makes possible easy installation and maintenance. The cascading also has flexible application scenarios.
- Vertical Sector Split
Vertical sector split leverages the widely available four-port dual-RET antenna that can be set with different tilts so that the original single sector in the same antenna is split to form two different sectors (Fig. 2). The vertical sector split solution can provide a capacity gain close to that obtained by the conventional horizontal sector split solution. Moreover, the vertical sector split solution can address the problems underlying in the horizontal sector split solution. It does not need to renew network planning, nor deploy new antennas. Instead, X-Site can be deployed overnight and quickly delivers mobile services. X-Site also uses a full array of interference cancellation solutions to eliminate interferences introduced in GSM, UMTS and LTE respectively to an acceptable low level. This ensures that the vertical sector split solution is flexible, cost-efficient, and also has high performance.
X-Site has innovative X antennas that can switch freely between three-sector mode and six-sector mode by dynamically adjusting lobe width. This gives operators one more solution for easy and smooth evolution to 4×4 MIMO without any investment waste. Using NMS software to monitor in a real-time manner basic network conditions (such as the penetration rate of 4×4 MIMO terminals), operators can switch with ease and efficiency to the evolution network when conditions are satisfied.
Trials and Results
X-Site has been put into trials in overseas markets. A leading operator in Indonesia is among the first ones to run an X-Site trial. The recent joint UMTS test by the operator and ZTE has shown that the X-Site solution can significantly increase voice capacity by up to 33% and data capacity by up to 32% and 44% respectively in HSDPA and HSUPA.
X-Site is an innovative site solution with high flexibility, efficiency and performance that can help operators worldwide make smooth evolution from UMTS or low-order MIMO LTE to high-order MIMO LTE. X-Site outperforms other alternative solutions in each key sector of the evolution process and will certainly help operators increase their competitiveness in the competition.