“Forgotten” communication standards: WiMAX, CDMA, ALOHAnet and others

The first transatlantic cable connected Europe and the United States in 1858, replacing shipping traffic, and the time needed to establish communications between continents was reduced from ten days to a few hours. By 1965, four hundred telephone channels had already been laid between the two continents.

Today we can not only instantly call any country, but also transmit video and photos, receiving data even from space. All these achievements owe their appearance to the evolution of communications. In the complex process of competition, some technologies inevitably lost out. But were they really worse, or were communication technologies “dying” for other reasons?

ALOHAnet

It was the first computer network to use wireless data transmission technology, which became the basis for the subsequent development of Ethernet, Wi-Fi and cellular networks.
ALOHAnet was developed by a group of scientists at the University of Hawaii who used ultra-high frequency radio stations to create the network. The development team decided that they needed to find a way for each communication terminal to use the same frequency. In other words, all terminals had to talk on the same "wire" at the same time.

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To prevent the “collision” of several messages, the first protocol for concurrent access to a communication channel was invented, which later began to be used in Ethernet and Wi-Fi networks.

ALOHAnet was ahead of its time and had a lasting impact on future technology solutions. Development of the network began in 1968, and in 1971 ALOHAnet began operating in the state of Hawaii. However, not a single company used it for commercial purposes - no one at that moment could appreciate what an important problem the new technology solved.

History of technology

Despite its promise and safety, this standard is not used very often. And many people ask the following question: “CDMA phone – what is it?” Its history began back in the 30s of the last century.

In the USSR, the famous academician D.V. Ageev carried out relevant research. In 1935, he published his own work, Code Channel Separation. The brochure did not become a bestseller because... was more related to future developments. But soon this topic was picked up by other famous scientists. This created the initial basis for the further development of CDMA technology.

Already in the late 50s, this standard was used in the USA for military purposes. It was only in the 80s that the technology was declassified and presented to the world. Dr. Irwin Marc Jacobs was able to adapt it. Later, he even created his own company, Qualcomm, dealing with satellite communications, telephony and cellular systems.

Thanks to this American, since 1992, the new standard has been actively implemented throughout the world. And since 1996, CDMA-GSM phones began to be used equally. Moreover, at that time, about 24 countries of the world participated in the project.

Code Division Multiple Access (CDMA)

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GSM and CDMA are different ways of achieving the same goal. Ultimately, the answer to the question “which is better?” lies in the quality of the operator’s infrastructure - whoever has a better network and wider coverage is the winner. Technically, neither of these standards is significantly superior to the other.

The difference between GSM and CDMA was in the data transmission methods: GPRS (General Packet Radio Service) in GSM provided slower throughput than CDMA (1xRTT - One Times Radio Transmission Technology), which was able to operate at speeds of up to 144 Kbps.

But CDMA had its drawbacks: 1xRTT technology requires a dedicated connection to the network, while GPRS sends packets, so accessing data on GSM phones does not block voice calls as it does on CDMA phones.

Moreover, in GSM you can easily change the SIM card of your phone. In CDMA networks, the necessary data was written (flashed) into the phone, but there was no SIM card. The CDMA phone could not be used while roaming. An analogue of SIM for CDMA phones - the so-called R-UIM - appeared only in 2002.

GSM and CDMA are incompatible with each other, so users are locked into this network. While Europe quickly switched to GSM, in the US, subscribers of several operators found themselves “hostage” to CDMA. At the same time, in Europe, communications have become cheaper and coverage is better.

The more advanced CDMA required more computing power and massive financial investments, while the GSM infrastructure was already established in Europe and Asia and did not require significant financial investments to maintain. All these factors led to a gradual decline in interest in the development of CDMA.

In 1996, the mobile operator Sonet was the first in Russia to receive a license to provide communication services in the CDMA standard. Just two years later, based on Qualcomm equipment, the CDMA network began operating in Moscow. In the second half of the 90s, scattered CDMA networks began to appear throughout Russia. By 2003, there were 350,000 registered users of CDMA networks (less than 2% of the entire Russian subscriber base), with 40% of them located in the Central Federal District.

The Sonet network ceased to exist in 2004 due to the refusal to renew the license for the 800 MHz frequency range, where the original CDMA 800 network operated. These frequencies were planned to be used for the development of digital television.

In 2002, a network built according to the CDMA2000 standard in the 450 MHz band went into operation and became its operator. At the time of launch, the company claimed that "this technology [CDMA2000] is 7.5 times more efficient in using frequency resources than GSM."

However, the growth rate of the subscriber base began to decline and by 2006 “did not meet even the most pessimistic forecasts.” The decline of CDMA lasted for many years - the last operator of the standard in our country stopped working in 2021.

Benefits [ edit | edit code]

• Flexible resource allocation. With code division there is no strict limitation on the number of channels. As the number of subscribers increases, the probability of decoding errors gradually increases, which leads to a decrease in channel quality, but not to service failure.
• Higher security (secrecy) of channels. It is very difficult to select the desired channel without knowing its code. The entire frequency band is uniformly filled with a noise-like signal.
• CDMA phones have lower peak radiation power and therefore allow more economical battery consumption.

Circuit Switched Data (CSD)

A data transmission technology from the 1990s that was used in GSM networks before the advent of GPRS.
For the first time, it made it possible to transmit digital data and connect to the Internet (with per-minute billing) at a speed of 9.6 Kbps. Before CSD, data transfer in mobile phones was carried out (when connected to an external modem) at speeds of up to 2.4 Kbps (from the definition of the GSM standard from May 1996).

Improvements in technology led to the advent of High-Speed ​​Circuit-Switched Data (HSCSD), in which the speed increased to 14.4 Kbps, and through the use of four parallel channels, the speed increased to 57.6 Kbps.

CSD technology finally died out when most telecommunications companies abandoned CSD support and switched to GPRS and EDGE (E-GPRS), which use more advanced signal encoding techniques to increase bandwidth.

What is GSM?

Much more is known about CDMA's main competitor. It is the one that is actively used in the work of domestic cellular networks. The GSM standard uses TDMA technology and is based on a frequency division channel algorithm. There are four ranges:

• Single-band. Used extremely rarely.
• Dual band. Here phones are tied to a specific region.
• Tri-band. The standards used are 900/1800/1900, as well as 850/1800/1900.
• Quad-band. Almost all new smartphones are provided with this functionality.

Worldwide Interoperability for Microwave Access (WiMAX)

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For the fourth generation (4G) network market, several wireless communication standards have been developed, including WiMAX. This technology had many advantages: throughput up to 75 Mbit/s, range of 25-80 kilometers, ease of deployment and easy scalability.

Of all the standards developed for 4G, WiMAX is the closest (in technology) to Wi-Fi. The standard, developed in 2001, is sometimes called "Wi-Fi on steroids" for its much higher throughput compared to Wi-Fi networks.

In 2005, the standard was updated to 802.16d (“Fixed WiMax”), providing a stunning speed of 25 Mbps for its time. This made it possible to conduct video conferences without lags and watch streaming video in HD quality.

An upgrade to 802.16m (“Mobile WiMax”) in 2011 provided speeds of up to 1 gigabit per second. It should be noted that the capacity of the WiMAX network depends on the number of users - the more connections, the lower the data transfer speed.

The WiMAX standard has been considered a good replacement for traditional terrestrial cable infrastructure for some time. Due to its long range and relatively low cost of implementation (compared to 3G, xDSL telephone network or hybrid optical-coaxial network), the technology could not only successfully compete with other standards, but also solve the problem of the “last mile” in remote regions.

Let us recall that the last mile in communication is the channel connecting the last network node of the provider and the client’s end equipment. Such a channel can be created using xDSL, WiMAX, FTTx (fiber to the x) and Wi-Fi technologies.

The first WiMAX network in Russia was launched by Yota in 2008 in Moscow and St. Petersburg. A total of 150 base stations operating in the 2.5 - 2.7 GHz range were installed in two cities. In the first year, the number of users of the new technology reached several hundred thousand.

In 2011, analysts at J'son & Partners expressed a pessimistic assumption that LTE would “kill” WiMAX in the coming years, but in Russia the network was doing well - WiMAX operators made big plans for further development. The frequency licensing problems that CDMA operators faced were not present here: the frequencies 2.3, 2.5 and 3.5 GHz were completely open for the deployment of the mobile version of WiMAX.

In 2012, Yota abandoned WiMAX, successfully “transplanting” its users to Russia’s first LTE network. The coverage of LTE base stations provided a more comfortable service area and provided Yota customers with a qualitatively new level of communication compared to WiMAX.

Today, large companies have already curtailed WiMAX software development and switched to LTE.

Smartphones

In this part of the section, we will discuss dual-standard smartphones. At the moment, both second-generation standards described above are widespread throughout the world and cannot be used simultaneously - but there is one exception.

These are special devices designed for use in two networks simultaneously - the capabilities are expanded by installing special software. Smartphones are equipped with the ability to receive signals in two different ways, specific to these networks.

There are quite a large number of smartphone manufacturers offering dual-band products with two SIM cards - these are giants such as Xiaomi, Lenovo, Huawei, HTC and many others. In addition, you can purchase a modem that operates in the desired range.

Rare Asian standards: PHS and PDC

Developed back in 1989 by Nippon Telegraph and Telephone Corporation, the Personal Handyphone System (PHS) standard was actively implemented in Japan and other Asian countries.
PHS used compact cells, with base stations with a power of up to 500 mW and a range of up to hundreds of meters (some models had a radius of up to 2 km). It all started successfully: easy deployment of networks, low fixed tariffs and good communications even in the metro - all this had a beneficial effect on commercial development. However, competing standards quickly achieved similar call quality, and the difference between PHS and GSM phones became blurred.

In 2010, PHS had 4 million subscribers (not all of them were active). Moreover, even in 2011, phones were released that supported PHS.

Another standard popular in Japan is Personal Digital Cellular (PDC). Belonged to the 2G generation and provided a data transfer speed of 11.2 Kbps. Japan could have participated in the development of an international communications standard, but preferred to support the development of the national telecom industry.

When PDC appeared, it quickly took over the entire Japanese domestic market. This resulted in incompatibility of Japanese telecommunications products with the GSM standard, which became dominant in the 2G era. Japanese telecom companies were thus cut off from the huge foreign market.

Long-term investment in their own infrastructure has also made Japanese companies too vulnerable to external competition. Not only companies promoting GSM were able to take advantage of this situation: the W-CDMA standard has also become widespread in Japan.

Wideband Code Division Multiple Access (W-CDMA) technology provides broadband access at speeds up to 2 Mbit/s. Those who travel a lot around the world have found themselves in situations where a mobile phone could only connect to a W-CDMA network - this standard is still relevant. As of 2021, W-CDMA covered about 65% of the world's population (LTE - 40%, and GSM - more than 90%).

Dual standard phones

As you can see from the article, both CDMA and GSM have their strengths and weaknesses. But for our people, it’s simply vital to use everything at once. That is why the dual-standard CDMA-GSM phone was invented. It combines all the advantages of both systems.

What is he? This is a completely ordinary mobile phone with an improved battery that can withstand more calls and conversations. In design and functionality, it is practically no different from its standard relatives.

Such cell phones have recently become increasingly popular. Therefore, gradually all the world's mobile brands began to produce separate lines of two-standard gadgets.

Other “forgotten”

It may seem that old technologies have long since become obsolete and are mentioned only in textbooks.
But this is a misconception: according to the Pew Research Center, back in 2015, 3% of Americans used dial up to connect to the Internet. This means that millions of people used the network at speeds of up to 56.6 Kbps. There are also rare new (or updated) niche communication standards. Everyone has heard about 5G, but there is, for example, DECT-2020 on the market - a promising standard that represents the next stage in the evolution of old wireless radiotelephones.

Conclusion

The article describes in detail what CDMA is. The standard gained high popularity in the early and mid-2000s due to its high communication quality, security and data transfer speed. In modern realities, CDMA is inferior in the capabilities of the LTE network, which remains the most dominant in the telecommunications services market. This is partly due to its high prevalence and compatibility with mobile devices.

What questions do you still have? Ask and share your opinion in the comments below the article.

First generation - 1G

All first-generation standards were analog and had a lot of shortcomings. There were problems with both signal quality and technology compatibility. Among the first generation mobile communication standards, the most widely used are the following: • AMPS (Advanced Mobile Phone Service). Used in the USA, Canada, Australia and South America; • TACS (Total Access Communications System) Used in European countries such as England, Italy, Spain, Austria and a number of other countries; • NMT (Nordic Mobile Telephone – Nordic mobile phone). Used in Scandinavian countries. • TZ-801 (TZ-802,TZ-803), developed in Japan. Despite existing problems with quality and compatibility of standards, analogue mobile communication networks have still found commercial application. The Japanese were the first to do this in 1979, then in 1981 the analogue network was launched in Denmark, Finland, Norway and Sweden, and in 1983 in the USA.

Frequency distribution of the 450 MHz range in the World

What are the main differences?

The key difference between these standards is the way they work with frequency resources.

GSM uses time and frequency separation of channels. Each subscriber is allocated a small frequency band on which the phone communicates with the base station. In this case, data exchange “sessions” are fixed in time. With a certain simplification, we will say that the signal is interrupted, but due to the high frequency of data transmission, the subscriber does not notice this. In real life, interruptions are noticeable only by the characteristic beeping sound of the speakers when there is a phone nearby that receives a call or a message.

In turn, CDMA uses code division of signals. Each subscriber connected to the base station uses the entire available frequency resource, common to all subscribers, and the base station communicates with everyone at the same time. The signal from a specific user is isolated using code modulation - each subscriber is assigned a specific “code”, which allows it to be distinguished from the general radio broadcast.

It is easier to describe different circuits with one simple example. Let's imagine that there are several people in the room, divided into pairs. The first part communicates in the same language, they speak in turns, for example, for 20 seconds - this is a description of GSM. The second part speaks simultaneously, but in different languages ​​- this is CDMA. In both cases, people communicate normally, but continuous conversation is obviously more comfortable, especially since the neighbors simply do not understand what they are talking about nearby.