ZTE’s Perspective on Top-Ten New Wireless Technologies for 2015

Mobile internet and internet of things (IoT) are developing at lightning speed and spurring the growth of mobile data services. More diverse communication, better user experience, and more extensive applications are development trends. To handle mass data traffic, mobile networks need to evolve into wireless networks without limitations. They need to become so-called “big pipes”. Breakthroughs are continually being made with wireless technologies as a result of more diverse applications and a renewed focus on user experience.
ZTE is a leading proponent of innovation and research on future-proof technologies, especially in the field of 5G. Here we discuss the top ten wireless technologies that ZTE will be watching with great interest in 2015.

New Multiple Access
5G applications will focus on mobile broadband and IoT, both of which require wider coverage, higher capacity, lower latency, and mass connections. It is therefore imperative to introduce new multiple access (NMA) for 5G. ZTE has proposed multi-user shared access (MUSA) based on the more advanced non-orthogonal multi-user information theory. MUSA is different from various orthogonal and quasi-orthogonal multiple access schemes (TDMA, CDMA, and OFDMA) currently used in mainstream wireless systems.
MUSA has innovative complex-field multielement codes and advanced multi-user detection based on successive interference cancellation (SIC). In the uplink, MUSA enables the system to reliably access several users using the same time-frequency resource and simplifies resource scheduling. This greatly simplifies mass access, shortens access time, and reduces terminal power consumption. In the downlink, MUSA uses innovative enhanced superposition coding and overlapped symbol-extension technologies to provide downlink transmission at higher capacity than mainstream orthogonal multiple-access schemes. This also greatly simplifies access and reduces terminal power consumption.

New Coding Modulation and Link Adaptation
Traditional link-adaptation technology is no longer adequate for 5G. New coding modulation and link-adaptation technologies can significantly improve system capacity, reduce transmission delay, increase transmission reliability, and allow access to more users. ZTE has proposed soft link adaptation (SLA), physical layer packet coding (PLPC), and Gbps high speed decoder (GHD).
SLA increases the accuracy of channel prediction and feedback, eliminates long-period and burst interference of open-loop link adaptation (OLLA), and satisfies various QoS requirements (e.g., low latency, ultra reliability, high throughput, or high-speed mobility) in new scenarios. PLPC resolves the contradiction between large data packets and small coded blocks. GHD can significantly increase speed for a single user and provide high data rates for 5G.

Massive MIMO
To handle explosive traffic growth, wireless network capacity can be upgraded by increasing spectral efficiency, network density, and system bandwidth and by intelligently offloading services. Large-scale antenna array technology has attracted more and more attention.
With a large-scale antenna array, tens to thousands of arrays at the base station side are configured for more accurate beam control than is traditionally possible with less than eight antenna arrays. A large-scale antenna array uses the same time-frequency resources as a traditional array but also uses space multiplexing to serve more users and improve spectral efficiency. A large-scale antenna array significantly suppresses intra-cell and inter-cell interference and increases system capacity and coverage.
More research is needed on the huge potential gains of large-scale antenna array technology, especially in the areas of channel information acquisition, array design, and codebook design. ZTE has competitive advantages in wireless technology. In November 2014, ZTE partnered with China Mobile to conduct pre-commercial field tests on the world’s first 128-antenna massive MIMO base stations.

HF Communication
The wireless spectrum below 6 GHz is very crowded and available bandwidth is limited. However, there is a large amount of spectrum available between 30 GHz and 300 GHz, which is quite attractive for wireless communications. Compared with carrier frequencies in existing cellular networks, millimeter-wave frequencies result in big transmission loss. Because the wavelength of high frequencies is short, more antennas per unit area can be configured so that transmitters and receivers obtain greater beamforming gains and compensate for extra path loss.

With a high-gain antenna base station, optimal beams cannot be used to cover the receiving end before their weights are obtained. Because the terminal measurement is not accurate, the two parties cannot communicate by means of the weights of optimal beams. It is difficult to identify high-gain narrow beams within a mobile environment. If optimal beams cannot be identified, the terminal will either not reside in the cell or it will reside in the cell but experience poor transmission quality. This is contrary to the high rates expected in 5G networks. Beam identification and tracking is a common problem in high-frequency communication. A beam-discovery process is therefore added to high-frequency communication so that the base station and terminal can find each other and use optimal beams for high-rate data communication.

Wireless Self-Backhaul
Wired backhaul makes the cost of dense base station deployment unacceptable and may make deployment very inflexible. Microwave backhaul requires additional spectrum resources and increases the cost of transmission nodes. When there are obstacles, the quality of the microwave channel is seriously affected. This makes it difficult to select appropriate base station sites and reduces the flexibility of base station deployment.
With self-backhaul, wireless transmission technology and frequency resources are shared with an access link and are used to solve problems in the wired or microwave backhaul. However, self-backhaul consumes the available resources of the access link and may limit network capacity expansion. Therefore, increasing self-backhaul capacity is an important research direction in the field of ultra-dense networking.
Increasing self-backhaul capacity involves using multi-antenna technology to
● further increase spatial freedom
● improve receiving capacity through coordination with receivers
● tap the same service requests with content-aware technology and improve resource efficiency through multicasting and broadcasting
● dynamically allocate resources between the backhaul and access links.

Virtual Cell
Virtual cell is the key to solving the cell-edge problem. At its core, virtual cells provide user-centered services. A virtual cell comprises multiple access nodes around a user. A virtual cell updates fast—like a shadow that follows a user’s movements and changes with the surrounding environment. This enables a user to access stable data services and have a consistent experience wherever they are.
Virtual cell turns a traditional cell-centered mobile access network into a user-centered mobile access network. Each user has a user-related virtual cell comprising several physical cells around the user. The physical cells coordinate with each other and serve the user together. When the user moves within the network, the physical cells contained in the virtual cell change dynamically, and the virtual cell ID is unchanged. Because no handover occurs during the movement, the user experiences good signal coverage from surrounding physical cells and the best access service wherever they are. Virtual cell is a revolution in mobile access. Before, the user had to search for a network; now, the network finds the user.

Ultra-Broadband Radio Unit
According to statistics, 83% of operators in 14 countries in Europe have 1.8/2.1 GHz dual-band. Large- and medium-sized operators in Europe have multiple mobile-spectrum licenses. Convergence of operators may greatly increase the sharing of wireless infrastructure, which is gradually evolving from broadband to ultra-broadband.
Ultra-broadband radio (UBR) supporting multiple bands will develop rapidly in 2015. UBR breaks through the constraint of one RF channel supporting only one band. UBR provides ultra-broadband processing for dual-band or multi-band operation. Its core technologies are ultra-broadband transceiver, ultra-broadband amplifier, ultra-broadband DPD, and collaborative duplexing. In 2014, ZTE launched a UBR unit operating at 1.8 GHz and 2.1 GHz. A single channel with transmission bandwidth of 365 MHz can support dual-band 1.8/2.1 GHz and enable power sharing between the two bands.

Fat NodeB
Fat NodeB is a new network node that can be networked with traditional base stations. It enables flat network architecture and can be used in complex scenarios.
Fat NodeB integrates the control-plane functions of a core network. This significantly shortens the time needed for terminals to access signaling. The core network only needs to focus on core services that are independent of wireless standards, and this makes it easier to provide personalized services. Fat NodeB also integrates gateway functions of a core network. Traffic from the terminal can directly enter a PDN via the fat NodeB without backhauling to a remote core network gateway. This alleviates the forwarding load on the user plane of a core network and reduces transmission cost. Moreover, moving the gateway down to the NodeB also enables content to be localized. Co-siting content servers and fat NodeBs enables terminals to access content nearby. This greatly reduces transmission delay and improves user experience.
ZTE’s fat NodeB solution leverages the idea of a flat, user-centered 4G network. It makes services and networks flatter and closer to the end user.
NFV/SDN
Because there are many dedicated devices in circulation, construction and OAM costs of traditional telecom networks are high, and traditional telecom networks provide more close services than IT networks do. Operators are therefore faced with a dilemma of unbalanced income and expenditure. Network function virtualization (NFV) and software defined networking (SDN) are a new ray of hope for operators.
NFV involves virtualizing server-related computing, storage, and networking resources into multiple (different) virtual machines for different users. NFV can be used in a telecom network to share hardware resources, improve resource efficiency, and rapidly introduce new third-party services. Through NFV, the telecom network decouples the dedicated hardware devices and makes it possible to use IT and universal hardware resources in the network. This helps operators reduce hardware purchase costs.
SDN derives from routing control of an IP network. By separating control from forwarding, SDN enables a large amount of complex routing configuration to be centralized via the controller, and this routing configuration is sent to the forwarding plane for execution. This greatly simplifies network routing maintenance. By opening northbound interfaces, SDN also enables third-party apps to easily control service routing in the network. SDN can be used in a telecom network to improve automatic network deployment and flexibly dispatch service-based components. SDN can also be introduced into mobile network nodes, such as SAE GW, to make a flat network and increase packet-forwarding efficiency.

Device-to-Device Communication
Device-to-device (D2D) communication is a candidate technology for 5G. It has received widespread attention in the industry for its potential to improve system performance and user experience and expand cellular communication applications. D2D can be used for
● social applications. With D2D discovery and communication functions, a user can look for another interesting user in the neighboring area for data transmission and sharing.
● network traffic offloading. Cellular communication between adjacent users can be switched to D2D mode. This saves air interface resource and reduces transmission load on the core network.

● IoT enhancement. In the internet of vehicles and smart home, where there are many terminals, the terminals are connected in D2D mode to specific terminals that have already accessed the network. In this way, the congestion caused by mass terminal access can be relieved.
● emergency response. In the event of network damage caused by blind area coverage or disasters, user devices can be connected to the user devices in the coverage area through D2D and finally be connected to the target network.