Application Technology of OFDM Broadband Wireless Access System

The goal of network development is to achieve better performance, wider bandwidth, and lower costs. I am wondering if I want to introduce a broadband wireless access technology and orthogonal frequency division multiplexing (OFDM). The birth of this technology will bring new prospects for the future wireless access technology.

One of the main requirements of the next-generation Broadband Wireless Access System (BWA) is to operate and maintain efficient performance under the conditions of OLOS or NLOS. Today, there are still many problems in network operations under OLOS and NLOS conditions, which limits the development of potential users by operators. Many early technologies are said to be able to provide some solutions, but later proved to be unconvinced because the single-carrier modulation method cannot solve the interference and multi-path problems in nl OS applications. Conversely, orthogonal frequency division multiplexing (OFDM)-a multi-carrier modulation technique that successfully transmits large amounts of data through radio waves, in addition, the broadband wireless access market announced that OFDM has achieved major technological breakthroughs.

Alvarion's BreezeACCESS OFDM production line is a new generation of broadband wireless access systems authorized to operate in the GHz band. This product is designed to meet the special needs of telecom operators and service providers.

1. performance and capability of non-line-of-sight applications

In real-world system deployment, terrain and landform conditions seriously affect the performance of the broadband wireless access system. In all practical deployment schemes, it is clear that different types of obstacles need to be considered. These obstacles may be caused by rural areas, suburbs, or dense urban terrain. In this regard, the powerful BWA system can work in a large range of links with high performance and efficiency. This capability allows operators to use a small number of base stations to cover a wider range.

BreezeACCESS OFDM is the first BWA system that supports NLOS operation in the GHz band. It uses the combination of OFDM modulation technology and dynamic adaptive modulation technology, which is the main factor for BreezeACCESS OFDM to operate with high performance, high efficiency and reliability under NLOS conditions. These capabilities have been proven in actual network links in multiple locations around the world.

2. Multi-path effects and spectrum efficiency

The BreezeACCESS OFDM system can work under the following environmental conditions: line of sight (LOS), line of sight (OLOS), and non-line of sight (NLOS. This is determined by the ability of orthogonal frequency division multiplexing (OFDM) technology to overcome the multi-path effect, which is particularly typical in the NLOS link. When there is an obstacle between the base station and the user location, the multi-path effect is generated. Under such conditions, the transmitted signal goes through multiple situations, such as reflection, diffraction, and scattering. The same signal passes through multiple transmission paths to reach the receiving end at different times.

The result of the multi-path phenomenon in wireless communication is the generation of ISI (symbol-to-symbol interference ). The echo of a definite symbol (called symbol n) is generated by the characteristics of the multi-path problem in the nl OS link. You can see the next symbol (called the symbol n + 1) interference. OFDM broadband wireless access technology uses the symbol's initial protection interval (GI) cycle to overcome the ISI problem. The protection interval can be interpreted as the part of the symbol damaged by the ISI. The data cycle at the protection interval carries the data load.

Using OFDM broadband wireless access technology, we can consider the use of high-speed data rates and high-efficiency spectrum. It is implemented through parallel transmission of multiple sub-carriers in the air. Each sub-carrier can carry the modulation data (the QAM 64 modulation method is used in BreezeACCESS OFDM ). These sub-carriers are all placed on orthogonal frequency points. Orthogonal means that at the center frequency, a certain sub-carrier and other sub-carriers have zero effect. The use of the orthogonal frequency concept avoids mutual interference between different sub-carriers, high-density sub-carrier configuration is ensured in the frequency range to achieve very efficient spectrum efficiency.

3. Provide better Network Interconnection

Maintaining the ability to work under the conditions of blocked line of sight (OLOS) or non-line of sight (NLOS) is crucial to using BWA as an access technology. It is understandable that operators need to know That BWA can be deployed anywhere and overcome various obstacles, such as mountains and trees in the countryside and buildings in the suburbs and intensive urban areas. These capabilities have taken into account different deployment situations from private residential users in the suburbs to offices and commercial institutions in the central cities, this allows operators to understand that using a single BWA system can satisfy the entire broadband access market.

The advantages of using a BWA System with NLOS capabilities include better coverage and penetration, which can provide B WA services for users who have not previously served, this allows operators/service providers to increase their potential revenue. It also reduces operating and installation costs. Because faster and simpler installation processes are adopted, it does not have to be required to work under the LOS condition, it also saves some additional ancillary equipment, such as the pole to be set up.

In short, BreezeACCESS OFDM can provide excellent broadband network interconnection under NLOS conditions. Alv arion has gained a lot of experience by using BreezeACCESS to deploy a BWA system. The features of this system have proved to be rich. For carriers and service providers wishing to deploy profitable GHz networks, it is ideal to use orthogonal frequency division multiplexing (OFDM) broadband wireless access technology to build networks.