WiMax bands

In recent years, the demand for broadband access is growing rapidly. WiMAX is a broadband wireless access technology (WBA-Wireless Broadband Access) built by the WiMAX Forum (WiMAX Forum) and aims to provide services from fixed to mobile. WiMax can provide Mbit / s speed to users (end-user) and within kilometers.

WiMax standards

In terms of standards, WiMax is a standard set based on IEEE's 802.16 family of standards but narrower and focused on certain configurations. There are currently two standards of WiMax: 802.16-2004, 802.16-2005.

The 802.16-2004 standard (formerly 802.16 REVd) was introduced by IEEE in July 2004. This standard uses OFDM modulation and can provide fixed, nomadic services (users can move but fixed during connection) follow straight vision (LOS) and do not follow straight vision (NLOS).

The 802.16-2005 standard (or 802.16e) was adopted by IEEE in December 2005. This standard uses modulation methods SOFDMA (Scalable Orthogonal Frequency Division Multiplexing), allowing the implementation of roaming and network functions, can provide simultaneous, nomadic and portable services (users It can move with walking speed), limited mobility and mobility.

Two duplex modes applied to WiMax are time-division duplex TDD (Time Division Duplexing) and duplex division by frequency (Frequency Division Duplexing). FDD needs 2 channels, one up, one down. With TDD, only one frequency channel, upstream and downstream traffic are divided by time slots.

Band for WiMax

The tapes focused by the WiMax Forum look at and mobilize the frequency management authorities for WiMax allocations: 3600-3800MHz, 3400-3600MHz (3.5GHz band), 3300-3400MHz (3.3GHz band), 2500- 2690MHz (2.5GHz band), 2300-2400MHz (2.3GHz band), 5725-5850MHz (5.8GHz band) and 700-800MHz band (less than 1GHz).

3400-3600MHz band (3.5GHz band)

3.5Ghz band is the band that is allocated by many countries for fixed wireless access system (Fixed Wireless Access - FWA) or for broadband wireless access system (WBA). WiMax is also considered a WBA technology so it can be used for WiMax. Therefore, that WiMax Forum agreed to select this band for WiMax.

WiMax systems in this band use the 802.16-2004 standard to provide fixed and nomadic applications, channel width of 3.5MHz or 7MHz, TDD or FDD duplex mode.

Some countries regulate this band only for systems that provide fixed services, no nomadic applications, so to implement WiMax it is necessary to revise this regulation.

For Vietnam, since this band is prioritized for Vinasat satellite system, it is currently not possible to deploy for WiMax.

3600-3800MHz tape

3600-3800MHz tape is considered by some European countries to grant to WBA. However, because part of this band (from 3.7-3.8GHz) is being used by many satellite systems (downlink C band), especially in Asia, it is less likely that this band will be accepted for WiMax in Asia.

Tape 3300-3400MHz (3.3 GHz band)

That band is allocated in India, China and Vietnam are considering a formal allocation. Since India and China are two major markets, even though not many countries have allocated this band to WBA, WiMAX equipment has also been produced.

The WiMax standard applied in this band is similar to the 3.5GHz band, which is fixed WiMax, FDD or TDD duplex mode, 3.5MHz or 7MHz channel width.

Since India only allows the use of the 3316-3400MHz frequency band, WiMax devices currently only work in this section with a maximum of 2x9 3.5MHz channels. Therefore, if the 4 operators use this band, then each operator is only allowed to use 2x2 3.5MHz channel. Meanwhile, in the opinion of Alvarion experts, one of the WiMax equipment providers, to exploit effectively, each operator should be granted at least 2x3 3.5MHz channels.

2500-2690MHz band (2.5 GHz band)

This band is the preferred band of choice for WiMax Forum for WiMax mobile according to 802.16-2005 standard. There are two reasons for this choice. First, compared to 3GHz bands, this band's transmission conditions are suitable for mobile applications. The second is the possibility that this band will be allowed by many countries to use WBA including WiMax. WiMax in this band has a channel width of 5MHz, a TDD and FDD duplex mode.

This band was previously commonly used for MMDS television systems around the world, but because MMDS did not develop, the 2000 World Wireless Information Conference (WRC-2000) was determined to be usable. This band is for 3rd generation mobile system (3G or IMT-2000 by ITU naming method). However, when IMT-2000 was deployed in this band, there was no clear answer. Therefore, there are a number of countries such as the US, Brazil, Mexico, Singapore, Canada, the United Kingdom (UK) and Australia that allow the use of this frequency band for WBA. China and India are also considering.

For example, Singapore has divided the 2.5GHz tape into 15 6 MHz blocks for WBA to bid, whereby operators are provided with fixed, nomadic and mobile services, which do not require the use of a specific technology. Come on. The winning bidders are responsible for coordinating themselves with each other and the operators of neighboring countries to avoid interference. In the US, the Federal Communications Commission (FCC) divides 2.5GHz into 8 blocks, each operator can get 22.5MHz, including a 16.5MHz wide spectrum combined with a 6MHz block.

Since ITU defines this band for IMT-2000, the WiMax Forum is planning to join the ITU research groups to promote the introduction of 802.16 as a branch of their IMT-2000 standard.

For Vietnam, the national radio spectrum plan approved by the Prime Minister at the end of 2005 has regulated the band 2500-2690 MHz will be used for new generation mobile systems, not implemented. Add other devices in this band. Therefore, it is understandable that mobile WiMax technology is also an object of this regulation, but this band will be used for which specific technology is still open.

2300-2400MHz tape (2.3 GHz band)

The 2.3GHz band also has the same transmission characteristics as the 2.5GHz band, so the band is considered by WiMax Forum for mobile WiMax.

Currently, some countries allocate this band to WBA such as Korea (deploying WiBro), Australia, America, Canada, Singapore. Singapore has auctioned 10 5MHz blocks in the range 2300-2350MHz to use for WBA with the same conditions as the 2.5GHz band. Australia divides this band into 7MHz blocks, without specifying the technology or channel width, giving priority to fixed applications. The US is divided into 5 blocks of 10MHz, not specifically specified for channel width, allowing the deployment of both TDD and FDD.

For Vietnam, this is also a likely band that will be used to deploy WBA / WiMax.

5725-5850MHz tape (5.8 GHz band)

This band is of interest to the WiMax Forum because it is a country with a lot of bandwidth that allows for unlicensed use and higher capacity than other bands in the 5GHz band (5125-5250MHz, 5250-5350MHz). , which is often used for indoor applications.
According to the WiMax Forum, this band is suitable for fixed WiMax deployment, the channel width is 10MHz, the duplex method used is TDD, no FDD.

Band below 1GHz

With lower frequencies, the farther the radio waves are, the less base stations need to use, the lower the level of investment for the system. Therefore, the WiMax Forum is also considering the possibility of using bands below 1GHz, especially 700-800MHz band.

Currently, some countries are making the transition from analog television to digital television, so it will solve part of the spectrum used for WBA / WiMax. For example, the United States has previously allocated a 699-741MHz frequency band for 52-59 UHF channel and considers 747-801MHz tape reception (60-69 UHF television channel).

For Vietnam, due to the nature of many local television stations, 470-806MHz channels for television are used heavily for similar television systems. There is currently no specific roadmap to convert these analogue television systems to digital television, so there is no possibility of a band to supply WBA / WiMax here.

What future of WiMax?

Due to the efforts of manufacturers in promoting, now WiMax is being talked about a lot, sometimes it is considered as technology to dominate the telecommunications market in the future, or 4G technology. But the fact is that WiMax is a technology in the process of being built and completed, there is no typical example of commercial success, so doubts about the success of this technology still exist. At (someone called this technology WhyMax instead of WiMax).

In the past 10 years, many wireless technologies have been heavily advertised, but little success has actually been achieved. In 1995-2000, low-range mobile satellite systems such as GlobalStar, Iridium, ICO, etc. were advertised as a great complement to terrestrial mobile systems, but practically all That system failed. The overestimation of the 3G system led to European operators pouring a large amount of money to reserve the right to use the band and then faced difficulties, even at risk of bankruptcy. WiFi in the early 2000s was also praised, but the limited coverage gap was immediately pointed out with the emergence of WiMax.

Therefore, the success of WiMax takes time to answer and management policies need to take into account this aspect. Many countries when allocating bands have adopted a technology independent policy, only specifying the purpose of not specifying the type of technology. The choice of the type of technology used in that band is decided by the operator itself and responsible.

Le Van Tuan