WiMAX has been one of the industry buzzwords of recent years promoted by many members of the industry chain. The technology, which is specifically oriented to provide mobile broadband services, has now overcome many of the obstacles it initially faced to commercial application so is WiMAX finally ready for commercial use on a large-scale? by Wu Yilin, Huawei Technologies
Currently, there is a popular outcry in many parts of the world for "broadband everywhere." In the past, many 2G subscribers were not very satisfied with wireless Internet access service, largely because of big differences in bandwidth when compared with wired broadband access services. Through cooperation between IT (internet technology) and CT (communications technology), WiFi turned out to be a great success yet WiFi was still far from realizing the goal of "broadband everywhere" due to its limitations with regards to coverage, security, operations and so on. WiMAX came into being largely in response to this situation.
WiMAX is a wireless broadband standard developed by IEEE?Institute of Electricaland Electromics Engineers? and the WiMAX Forum. The WiMAX Forum serves as a promoter for the WiMAX industry and has more than 450 members consisting of operators, vendors and industry organizations. The WiMAX standard includes a number of variants. The IEEE 802.16d standard only supports its fixed application, and the IEEE 802.16e standard, covers both its fixed and mobile applications.
The WiMAX standard has been gradually maturing since 2001. From its air interface to its network architecture, WiMAX exhibits its superiority in almost very aspect. For instance, by using technologies such as OFDMA (Orthogonal Frequency Division Multiple Access), MIMO (Multiple-Input Multiple-Out-put ), AAS (Adaptive Antenna System) and AMC (Adaptive Modulation and Coding), the air interface takes the leading position in such aspects as capacity, coverage, and spectrum efficiency. What's more, the network has a flat All-IP architecture, which helps to reduce operators' CAPEX/OPEX, and also reflects the trend towards the emergence of the radio access network.
Massive investment in the technology in recent years has caused the price of the average WiMAX chip to drop drastically. This price reduction will certainly help to remove the largest obstacle to the commercial use of WiMAX – cost.
The second largest bottleneck in achieving the objective of "broadband everywhere" previously lay with subscribers' handsets. It has only been in recent years that the IT industry has seen the required technical progress and increased awareness in the requirements of personal communication devices. Only now have mobile Internet terminals seen the development from Ultra Mobile PC (UMPC) to Mobile Internet Device (MID), and become available more elegant, with better features, and at a reasonable price.
So WiMAX has gained wide-ranging support from many people in the industry. The end-to-end industry chain has been developing quickly in recent years, and problems relating to its standard maturity, equipment cost, and terminal bottlenecks have for the most part been solved. Nevertheless, as an emerging wireless access technology, WiMAX still has to face and overcome a number of other challenges before its successful commercial use. Here are some of the most critical barriers to widespread adoption.
Enhance the coverage
Experience in wireless network construction, operation, and maintenance shows that a network's total cost of ownership (TCO) is directly related to the number of BS sites it contains. In other words, a network with a small number of BS sites has a lower TCO than one with many and is therefore more likely to be deployed. For WiMAX to be deployed commercially then, by the same reasoning, the number of WiMAX BS sites has to be kept minimal while ensuring excellent coverage capability.
There are a number of ways this can be done.
BS coverage can be enhanced with multi-antenna technology such as MIMO (Multiple-Input Multiple-Out-put) BF or by increasing the transmitting power of the BS, or enhancing the BS's receiver sensibility. Additionally, successful 3G network construction cases clearly show that, through the use of the distributed BS solutions, where the RRU can be installed near the antenna, attenuation on the long feeder and the number of tower mounted amplifiers (TMA) can be reduced. All of these measures will result in wider coverage for BSs.
Cut O&M costs
From macro BSs, which cover thousands of square kilometers, to home FemtoCell BSs, which cover hundreds of square meters, mobile BSs have become elements with the most variable forms in a mobile network because of the diversity of application scenarios. Therefore, a complete WiMAX solution must accommodate a series of BS forms such as an indoor/outdoor macro BS, distributed BS, Pico BS, and Femtocell BS to satisfy various networking scenarios. Due to the diversity of BS forms and systems, mobile operators, especially those who also own GSM mobile networks, all encounter a great deal of pressure relating to network maintenance.
One way to reduce the cost of network operation and maintenance is to share All-IP BSs, that can be used for WiMAX, with other technologies such as GSM, CDMA and WCDMA so that fewer spare parts and fewer maintenance personnel are required. Plus, co-sited BSs with different technologies can share transmission equipment, power, antennae and feeders, and can be seamlessly integrated with IP networks.
Reduce backhaul costs
Reducing the costs for BS backhaul has been a hard nut to crack for wireless network operators but achieving a reduction in the bearer cost is an important factor for successful WiMAX network operation.
Because of the diversity of access network transmission technologies, WiMAX BSs must be adaptive to various transmission resources. One way to reduce costs is to provide various interfaces in the form of a pinch board which can avoid using external stand-alone transmission equipment, help reduce construction costs and intermediate NEs (Network Element), and also enhance network reliability and minimize network management workloads on transmission equipment.
A second way to reduce bearer costs is to use transmission resources more efficiently. Using the header compression is an effective means, especially for VoIP services, of saving up to 60% in terms of bandwidth. WiMAX requires a great deal of transmission bandwidth, so there is little point-to-point transmission between the BS and the GW (gateway) however, by means of service statistical multiplexing on the bearer network, more bandwidth can be saved in comparison with compression.
Finally, operators can lower BS bearer costs through self-backhaul. Compared with microwave, self-backhaul supports point-to-multipoint transmission, which permits uniform maintenance and installation together with the WiMAX product. The self-backhaul also solves the problem of non-line-of-sight transmission to some extent. With an upgrade in software, the self-backhaul fulfills the WiMAX mesh function, which leads to much lower operation costs.
Diversified requirements need to be ironed out
Operators tend to differ considerably in WiMAX network construction and operation modes. WiMAX's successful commercial deployment depends on whether the operator implements it in the most effective way. There are three main ways this is currently being done. New operators should choose the version most applicable to them.
GSM operators that do not have a 3G license, and CDMA operators usually strive to acquire low-cost data solutions, hoping to protect their existing investment, while trying to maintain continuity in subscribers' service experiences. They are likely to introduce WiMAX, at least in the beginning stages, while continuing to use their existing mobile network, so WiMAX can provide voice services and low-cost data services while resource sharing (such as sites and transmission equipment). This lowers WiMAX network construction costs and allows the network to be quickly deployed. Later, the services of the two networks can be integrated, facilitating the introduction of new services to attract subscribers. Furthermore, subscribers' experiences will be improved and mobile broadband services will be extended by means of sharing the NMS (network management system), billing system, bills, and SIM authentication.
Fixed network operators often suffer due to limited copper cable resources at the network end, which inevitably leads to difficulty in acquiring new subscribers. Hence these operators are often willing to use the radio access network to help them lower network costs, to solve the problem of the last mile in terms of broadband access, and to provide voice and broadband data access. However, they would require that the radio access network be seamlessly integrated into the existing fixed voice and broadband network. This being the case, a WiMAX+NGN VoIP solution would be their best choice, because it allows end-to-end voice services with high quality of service (QoS). WiMAX will also help them to facilitate network construction, or can be used to access the broadband radio access server (BRAS) to provide broadband access capability, and allow integration with the existing fixed broadband access and enterprise VPN services.
New mobile operators, on the other hand, are usually more eager to acquire a low-cost and technically advanced mobile network in one quick stroke, which would give them the ability to attract more subscribers, even at the expense of having incomplete network coverage. To construct a new network, an IMS+WiMAX mode can be directly used, which, by means of end-to-end dynamic QoS, is able to provide a more reliable platform to help operators develop VoIP, VT and Mobile IPTV services, and to make various new services available more quickly. Moreover, by means of interworking with 2G operators, operators are able to provide subscribers with dual-mode terminals, thus, compensating for network coverage left over from the earlier phase, and it will also give operators the ability to acquire more and more subscribers quickly.
Thanks to WiMAX, the dream of "broadband everywhere" is not too far from becoming reality, but there are still a number challenges that need to be overcome before WiMAX is likely to be used commercially worldwide. As we have seen, several barriers existed in the past which have now been overcome; I believe it is only a matter of time before the others identified above are also conquered. We have walked several hundred miles on the road to WiMAX's full commercial use. We only have one mile to go.
