The traditional microwave frequency bands (6 to 42GHz) are almost depleted in the face of fast-growing mobile broadband (MBB) demand, making microwave expansion to the higher bands an inevitability. Enabling gigabit-per-second data rates, E-Band (80GHz) is abundant, capacious, affordable, and adaptable for dense deployment, making it a key trend in carrier-class wireless transmission.
E-Band for large-capacity backhaul
E-band is the conventional name of the portion of electromagnetic spectrum lying at 80GHz (71 to 76GHz and 81 to 86GHz), which is currently the highest frequency used for commercial telecommunication networks. With a 10GHz frequency band, E-band can be divided into 19 basic 250MHz channels, which can be flexibly combined and offer gigabit-range data rates. With higher-order modulation schemes, E-band can enable 1-to-5Gbps or even 10Gbps air interface capacities.
Assuming 400Mbps as a baseline requirement for the backhaul of a GSM/UMTS/LTE site (300Mbps for LTE services), traditional microwave (6 to 42GHz) must allocate the maximum 56MHz channel and use 256QAM to meet transmission requirements, making 400Mbps represents the maximum capacity enabled by traditional microwave, without using any capacity enhancement techniques.
E-band, on the other hand, can secure 400Mbps transmission by using QPSK in one 250MHz channel only. By using higher order modulations, such as 64QAM in a 500MHz channel (two 250MHz), E-Band can deliver a speed of about 2.5Gbps without effort. For a GSM/UMTS site in a live network, its capacity can generally reach 100Mbps; yet large traffic convergence links still need Gbps capacity to transport data to core networks, and E-Band is perfectly positioned for this scenario.
With the spectrum allocation at 80GHz, E-Band offers a number of benefits including the narrow pencil beam that enhance frequency reuse and interference protection, making it ideal for dense LTE site backhaul. When allocating microwave spectrum, operators can flexibly use one or combine multiple 250MHz channels, together with capacity enhanced technologies such as adaptive modulation (AM) and adaptive coding/channel spacing (AC), In this way, spectrum can be flexibly allocated in dense urban areas for backhaul purposes, and multiple operators can deploy E-Band microwave networks in the same area.
As of the end of 2012, over 40 markets globally opened their E-Band frequency resources. To encourage more applications, most markets offer free or slightly-charged E-Band frequency bands, easing the microwave spectrum shortage and reducing operator investment.
Existing E-Band microwave equipment is generally for enterprise applications, and has certain limits on transport capacity, spectrum efficiency, and network management. Deficiencies include the use of low modulations (such as BPSK); spectral inefficiency (1GHz is needed to reach Gbps speed); lack of support for packet transmission (any L2 or L3 feature is left to the switch or router that the radio is connected to); late/limited support for synchronous Ethernet; lack of support for IEEE1588v2; lack of carrier-class service guarantees; and very high costs (compared to 38GHz equipment) due to low volumes and expensive first- generation components.
Growing mobile broadband and LTE services are expected to push the transmission capacity of a single base station to the Gbps range, and LTE networks also demand greater synchronization and network management. First-generation E-Band, which focuses on enterprise applications, can hardly meet operator needs for carrier-class, low-cost backhaul.
In October 2012, Huawei launched the industry’s first second-generation E-Band microwave solution, representing a major upgrade in terms of capacity, transmission efficiency, clock synchronization, network management, and TCO reduction.
Second-generation E-Band supports 64QAM and can deliver 1.2Gbps transport without capacity enhancements such as header compression (which doubles the capacity when applied). Since it is possible to bundle more than one 250MHz channel, second-generation E-Band can easily reach a peak capacity of roughly 2.5Gbps using a 500MHz channel. Thanks to these features, Gbps backhaul per base station is assured for LTE.
Enhanced transmission efficiency
Adaptive modulation and adaptive channel size are now applied to second-generation E-Band, enhancing the capacity and reliability of microwave links, while minimizing the impact of bad weather and environmental changes. Second-generation E-Band also supports QPSK and 64QAM, six-grades working modes (to adapt to changing climatic conditions), dynamic band selection (250/500MHz), and bandwidth flexibility (from 100Mbps to 2.5Gbps).
Packet header compression (bandwidth acceleration) allows operators to equalize the transmission efficiency of small packets with that of larger packets, while increasing the equivalent throughput of the radio link. Second-generation E-Band compresses both the L2 (Ethernet) and L3 (UDP, IP, IPv4 and IPv6) headers going through the link, improving the transport efficiency for small packets (≤128Bytes) by 50 to 60%. As LTE services contain a large portion of small packets, second-generation E-Band can significantly enhance overall traffic transport efficiency.
Clock synchronization is a basic feature of mobile backhaul networks, but first-generation E-Band supports only Synchronous Ethernet for clock signal transference, which can hardly meet the phase synchronization needs of LTE services. Second-generation E-Band, while also supporting Synchronous Ethernet, enables IEEE 1588v2 transparent clock (TC), boundary clock (BC), and ordinary clock (OC) functionality. It also uses an out-of-band synchronization channel to ensure precise packet transport.
Simplified network management
Second-generation E-Band has abundant network management features, including extensive protection schemes for equipment, links and networks; full L2 switching; deep E2E QoS and SLA support; L2 OAM for troubleshooting; and MPLS-TP support to ensure E2E packet service transport and management.
There are a huge number of factors determining the actual TCO of a given technology. Besides significant spectrum cost savings, second-generation E-Band also delivers other key economic benefits such as carrier-class reliability, thanks to its design and components, as well as significantly enhanced efficiency in terms of capacity (cost/Mbps) and power consumption (W/Mbps), thanks to its vastly increased spectrum efficiency and achievable top speed. It also features a compact outdoor design and scalable GE interfaces, as well as timely deployment features such as USB-key configuration, one-for-all cable functionality (one cable for service provisioning, electricity, and network management). And finally, network management is unified for optical infrastructure, routers, and other microwave equipment.
According to Dell’Oro, ultra-high-capacity microwave revenue would grow at a 26% CAGR between 2012 and 2017. With second-generation E-Band, operators can build a high-quality ultra-broadband backhaul network and use it in high-bandwidth convergent links, as an add-on to optical transport networks, and in backhaul networks for micro base stations and small cells. Many operators have started commercial deployment of second-generation E-Band, including Vodafone, France Telecom, Deutsche Telekom, Telefónica, Telenor, and MegaFon.
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