CDMA STRENGTHENİNG POSİTİONS

 

Mobile communication system CDMA implemented last years in Azerbaijan is getting more and more popular among users. Number of subscribers of this network in Azerbaijan already exceeded ten thousand. Today this service covers the country's areas where 45 percent of the population resides. CDMA services are provided in five regions: Absheron, Ganja, Shamakhi, Lankaran and Shamkir. First CDMA service provider in Azerbaijan is Azerbaijani-American Joint Venture Catel.

 

Caspian Energy (CE): Mr Humbatov, could you provide detail on the history and development of CDMA technology?

Sadig Humbatov, CEO, Catel: The scientific basis for this most interesting radio communication technology was laid yet in 1930s. However neither hardware nor software of those days allowed putting in practice all sophisticated math algorithms required to create systems with code separation of channels.

Origination of radio equipment with code separation of channels principle is dated back to 1950s. This technology ab ovo was applied in US warfare within more than two decades. However element bases of that time, as well as imperfect software, insufficient funding of secret CDMA researches and relatively low capacities of code channel separation networks did not allow for using all advantages of new access method in full. In late 1980s, US Department of Defense declassified this technology and authorized its use in civil radio communication appliances (frequency 800 MHz). That date is considered the reference point for beginning of civil application of CDMA technology.

The broadband signal transmission method used in this technology and its unique interference immunity benefited significantly to capacity and efficiency of these radio frequencies.

The milestone in the widespread of this technology was 1989 when QUALCOMM has literally blown up the market by stating that CDMA technology enables raising analogue cellular networks capacity in 20 times. Successful field tests have proved this theory. IS-95 recommendations were embraced by Telecommunication Industry Association (TIA) and yet in 1992 turned into a standard of digital cellular radio telephone communication.

In September 1995 the world's first commercial CDMA network using base equipment from Motorola (base stations SC 9600 and switching equipment EMX 2500) and QUALCOMM's mobile phones were deployed in Hong Kong. By the end of 1996 this network incorporated 113 cells and provided services to more than 40,000 subscribers at a sole frequency channel with a bandwidth of 1.25 MHz. However these CDMA cells were overlaying existing AMPS network and mobile terminals were running in a dual mode: in case CDMA-networks failed the user terminal was automatically switched to AMPS (FDMA) network.

Apart from said standard (IS-95), its broadband version W-CDMA was developed in 1999 (Ericsson, Sweden) to operate within the range of 1,800 MHz. Due to its even greater throughput it is intended to be used in areas with high population density.

And by the end of ее century Europe faced the problem of digitalizing existing analogue cellular communication networks operated within the range of 450 MHz. As known, demand determines supply. And here, in late 2000 one more version of CDMA technology, CDMA-450 (or CDMA-2000) was introduced by US-based Lucent Technologies. This equipment combined all advantages of CDMA-800 and a far range of 450MHz analogue standards.

 

CE: How easy it was to promote CDMA technology in mobile communication market?

Sadig Humbatov: It is not said to be easy at all to boost CDMA technology in mobile communication services market. This new generation equipment faced serious opponents that did their best to prove the new communication channel separation method groundless and ineffective. However despite all obstacles this technology secured a decent place in the market and is confidently extending its geography. From the recent time Azerbaijani mobile communication lovers can also take the advantage of this state-of-the-art communication.

 

CE: What were the distinguishing features of this new technology that enable it getting so popular in oversaturated market?

Sadig Humbatov: This technology is differing utterly from other systems. For example, CDMA ensures high speech quality and it proves the first digital technology meeting the highest international standards. By its characteristics speech transmission quality is comparable with that of fixed phones, and it features zero interference, noise background or distortions in transferred information. The built-in encoding system provides a high degree of transferred information protection from unauthorized access or eavesdropping. CDMA technology enables to send facsimile messages and provide data transfer services.

In CDMA systems each voice stream is marked with its own unique code and transferred via one channel alongside many other encoded voice streams. Receiving side uses the same code to separate the signal from noise. This code is the only difference among numerous voice streams. As a rule, the channel is very wide and each voice stream is distributed across the whole bandwidth. This system comprises a number of 1.23MHz wide channels. The voice is encoded at a rate of 8.55 kbit/sec but voice activity determination and different encoding rates can reduce the data stream rate to 1,200 bit/sec. CDMA systems establish a very sustainable and protected connections despite an extremely low signal power; theoretically, the signal may be weaker than surrounding noise.

 

CE: What are CDMA advantages compared to other digital technologies?

Sadig Humbatov: CDMA technology provides high quality of speech and at the same time reduction of output and noise level. The result is a constant high quality of speech and data transmission with minimum average output. With hundredfold lower output compared to other currently used standards, CDMA technology is in advantage in respect to two important factors: impact to human organism and duration of work at one charge of battery.

CDMA's capacity is ten to twenty times higher than that of analogue systems and three to six times that of other digital systems. The networks built on its basis efficiently use radio frequency resource thanks to multiple use of same frequencies in the network.

By speech transmission quality CDMA can be compared with landline channels. Since CDMA channels transfer not only voice but any other information, low or zero interference is the matter of special importance. While ordinary user, in general, does not care whether his voice at phone conversation sounds perfectly or with some interferences, the errors in file transmission can impair integrity of, for instance, enterprise database. The "code" applied serves not only for identification of user's conversation, but is also a kind of a filter that eliminates distortions and background noise. The built-in encoding algorithm ensures the high degree of confidentiality through protection from unauthorized access and eavesdropping.

CDMA system allows shorter delay in voice message transfer than other mobile communication systems. With CDMA, one does not need to use any sophisticated means to suppress echo. The perfect error correction method efficiently suppresses the signal multipath. This feature gives additional benefits to CDMA in urban conditions of high buildings.

A subscriber does not want to stay out of range when a fax is being sent and phone busy long time. CDMA provides additional service of simultaneous voice and fax transmission via one channel. CDMA technology implements original data packaging algorithms for greater transmission speed.

 

CE: You said of the system security. Could you provide any detail?

Sadig Humbatov: Various studies showed that of all cellular communication technologies the most environment-friendly is CDMA.

Taking ecological and technical data of base stations, one should figure out the significant difference between performance of single base station and base station within the CDMA or GSM network. Individual sector of GSM-900 base station is able to service 7 users at once, while a standalone CDMA base station can maintain up to 61 information channels. In fact, we are having 20 to 25 talk channels. Comparing these figures with a network of any other standard where similar frequencies cannot be simultaneously used in adjacent cells and a frequency planning is required, CDMA network capacity proves greater in all equal conditions.

The features I mentioned are defining the main economic advantages of CDMA network: increase of coverage the cells provide at the launch and rise of network and cells capacity through planned penetration to the market. For example, "smooth switch" at least halves number of base stations deployed at the beginning of service provision, and CDMA network capacity is 3 to 5 times higher compared to TDMA (D-AMPS, GSM, DCS) and 10-20 times higher compared to analogue FDMA (AMPS, NMT).

The studies allowed for formulating the basic environmental and technical advantages of CDMA standard:

 

CE: So it appears that subscriber capacity of this technology is higher?

Sadig Humbatov: Here I should note that one cannot say CDMA technology prevails by both subscriber capacity and interference immunity. Speaking strictly, these are mutually exclusive characteristics. Where one rises, the other falls and vice versa. Nevertheless, in equality of all other conditions (size of service area, number of cells, population and distribution of subscribers) said characteristics of CDMA system outpace that of existing TDMA technology. And I hope this technology will, against all odds, secure with time a decent place in Azerbaijan's telecommunication market, which is evidenced by growth of demand for our services.