Cloud Radio: The Best Choice in the 4G Era

Key Techniques
Cloud radio uses
• enhanced X1 and X2+ interfaces. These are compatible with 3GPP interfaces and can be applied to all kinds of eNBs. X1 is an interface between an eNB and a center scheduler and only exists on the control panel. X2+ is an interface between eNBs and can enhance coordination between eNBs.
• cloud scheduler. This helps each cell gather all its time, space, frequency, and power resources and allocates them in a unified manner. It allows for consistent decision-making and controllable allocation. The cloud scheduler greatly reduces interference between cellular cells and improves cell throughput. Even in peak hours, it can increase the throughput of a cell edge by 30 percent. The cloud scheduler can be used in all kinds of backhaul and HetNet scenarios.
• lite coordination. Various Lite coordination technologies are used to improve system performance and lower transmission requirements. Soft-combine Lite using ARQ at a retransmission rate of 10 percent can reduce transmission delay tenfold. Cloud IRC can prevent interference in the uplink. This significantly improves the quality of received uplink signals, and the system can perform at half its capacity even if soft symbol data throughput is reduced by a factor of one thousand. JT-Lite and CS/CB/NF Lite can reduce transmission delay by a factor of some dozens by only introducing a delay of 1~N ms.
• super cell. This is formed by traditional neighboring cells that can use a wireless transmission solution. Dedicated resources such as cell ID, master-and-slave synchronization signals, frequency-hopping sequence, and scrambling sequence can be shared between these cells. In the CP, the super cell removes boundaries between macro and micro cells and between individual macro cells. This improves coordination between all cells. With a super cell, the drop rate of a physical downlink control channel is also reduced. When combined with the inter-CP SDMA technology, the super cell does not significantly affect system capacity.
• P-bridge. Advanced CPRI compression lifts fiber resource constraints. Existing Ethernet cables are reused for flexible p-RRU deployment. The photoelectric conversion module converts 10G optical fiber to GE cable. A P-bridge module can carry multiple p-RRUs, and the remote p-RRUs are directly powered by a P-bridge converter. This makes it easy to deploy p-RRUs. ZTE’s P-bridge solution uses the Ethernet frame format for data encapsulation so that routing and distance can be flexible expanded via an Ethernet switch.

Core Value
The core value of cloud radio lies in its adaptability and seamless coordination. Cloud radio can adapt to different transmission scenarios and perform optimally. Cloud radio based on ZTE’s SDR platform allows for the transmission network to be smoothly upgraded by software, and no hardware need be changed. With cutting-edge multilayer coordination technology, cloud radio considerably improves edge network performance, especially spectrum efficiency and transmission gain. All this helps enhance user experience. Traditional network coordination is based on the cluster. Coordination within a cluster is good, but coordination between clusters is bad. When a user is on the edge of a cluster, coordination is poor or even nonexistent. This results in unstable user experience. Cloud radio allows for dynamic, real-time coordination based on user location. In other words, the cluster being coordinated changes in real time according to the user’s location and feedback. With cloud radio, coordination is dynamic and continuous, and a user does not feel any change. 

Conclusion
ZTE’s innovative cloud radio allows operators to address interference and coordination that affect OAM and arise as a result of the coexistence of multistandard networks. Wireless network performance can be optimized for given bearer resources, and user experience can be significantly improved. Cloud radio also protects investment, increases revenue, and helps operators secure a leading position in the wireless market.
Operators in China, Japan, and India have chosen ZTE’s cloud radio to deploy their wireless networks and have benefited from it. In the near future, cloud radio will help more operators improve their wireless networks. ZTE believes cloud radio is the future of wireless networks.