Do you know wireless access technology?

The emergence of wireless access technology has brought tremendous changes to our lives. We are not constrained in various "lines. Now let's take a look at the wireless access technology in detail. The license-free mobile access (UMA) is a brand new second-level technology suitable for providing seamless voice services. It uses the mobile exchange center (MSC) of mobile operators) implement Call Control for GSM or broadband IP Access networks. Using a broadband IP network, GSM voice signaling and carrier can be tunneling over the IP network and return to the domain of the mobile operator. When a user moves in the Wi-Fi and GSM coverage areas, the Network transfers the call seamlessly. In a well-designed IP network, users will not experience service degradation. This technology is especially suitable for scenarios where Wi-Fi is needed in buildings to make up for mobile phone signals. It will be available in the next 12-18 months.

Mobile IP is a layer-3 technology applicable to laptop-based data services (without voice call control ). Swedish telecom (swisscom-mobile.ch) and other operators have long used the triple-mode PCMCIA card to support Wi-Fi, GPRS or UMTS wireless connection and provide services. The laptop selects the best wireless signal, and the mobile IP enables seamless transfer when users move between different wireless coverage areas. The advantage of a Mobile IP address is that it allows a laptop to retain its IP address when the user moves. This technology has been put into use and is deployed in many regions around the world.

Process Initiation Protocol (SIP) Application Layer Mobile is the future development direction of global service providers. It supports real-time multimedia services in the pure IP Smart terminal field. One major advantage of using SIP for service integration is that users can transmit application processes between devices. For example, a process can be started on a laptop at home. When a user leaves home, enters the car and sends it to the PDA and returns it to the laptop upon arrival in the office. SIP requires real-time, IP-based multimedia, which indeed requires a considerable investment in public wireless access technology. Therefore, it may take many years to launch. Integrating a variety of wireless access technologies into a seamless service poses technical challenges. Therefore, we need to examine its necessity.

The wireless access technology is based on the IEEE 802.11 standard. This technology is widely deployed, cost-effective, fast, and uses unlicensed spectrum. The latter has an important impact on the deployment method of the technology. The absence of a license does not mean that there is no management. The use of the unlicensed frequency band imposes a limit on the transmit power of 802.11 wireless devices. The higher the output power, the higher the risk of interfering with other users in this band. To sum up, this technology is mainly used to support wireless LAN services. These services include a single access point in a cafe and a large number of access points covering the entire airport or downtown area.

Wireless access technology usually has performance advantages in mobile services, which is inseparable from the physical features of radio. The RF signal intensity degrades with the increase of distance (in some places or even faster ). Therefore, the closer the user is to the access point, the stronger the signal, and the higher the service performance. Public wireless access technology is usually used in areas with high traffic (such as hotels, airports, and conference centers). It only needs to transmit signals to hundreds of feet. Mobile Wireless Services must transmit signals over dozens of kilometers.

One advantage of Wireless LAN over mobile services is the channel width of the carrier. The wireless LAN operates in a higher frequency band and uses a wider channel. The current system uses a 20-MHz channel, which is likely to include wider and narrower channel options in the future. A wider channel supports a higher data rate. Although a higher frequency band does not have the same penetration power as a cellular band, this is undoubtedly an advantage when using a non-licensed frequency because it helps to limit interference.

On the contrary, the wireless WAN (mobile) system runs in a lower frequency band and has a narrow channel. A narrow channel means a low rate, which is mainly caused by the low cost of RF spectrum. A lower spectrum is far more valuable than a higher frequency and can be run in a narrow channel width.

The ideal frequency for mobile applications is less than 1 GHz. in fact, mobile services running at 450 MHz have been successful all over the world, the area covered by a honeycomb tower is the same as that covered by dozens of towers running at 1.9 GHz (varies by region ). In addition to a larger scope of transmission, a lower frequency can penetrate the structure more effectively, so as to facilitate users in the deep layer of the building. This is critical to carriers and users who require ubiquitous connections.