Fifty years with mobile phones From novelty to no. 1 consumer ...
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Fifty years with mobile phones From novelty to no. 1 consumer ... Document Transcript

  • 1. Fifty years with mobile phones From novelty to no. 1 consumer product Olof Billström, Lars Cederquist, Magnus Ewerbring, Gunnar Sandegren and Jan Uddenfeldt This year marks fifty years since Ericsson introduced the world’s first au- developed and inaugurated in Great Brit- tomatic mobile telephone system for a few hundred subscribers in Stock- ain in 1985. Ericsson manufactured equip- holm and Göteborg (Gothenburg), Sweden. The associated mobile units ment for each of these standards and quickly were colossal 40kg blocks of radio equipment designed for installation in grabbed a 40% global market share of analog the baggage compartment of a car. systems. In fact, Ericsson was the first sup- The extraordinary success of mobile communications, from those early plier to take a TACS system into operation pioneering efforts to today’s miniature telephones and advanced services (for Racal, currently Vodafone). – the result of global technical labors of the highest art – reads like a page These early systems were all analog sys- tems based on frequency-division multiple from a storybook. From the outset, Ericsson has been a major player, driv- access (FDMA) technology, which allocates ing many facets of development and helping to create the standards that a distinct frequency channel to each user. prevail in the industry today. Today, we think of these standards as first- The expertise Ericsson gained from its first systems, and a steady ambi- generation (1G) mobile systems, but in their tion to create an optimum, automatic network, laid the groundwork for a day they were considered fourth-generation vision that has stood the test of time. Ericsson continues to forge ahead as systems. We would remind the reader that a technical leader in the field of mobile communications – perhaps more the systems were designed for telephony so now than ever before thanks to high-speed packet access (HSPA), the from cars – apart from the handset, all mo- turbo version of the 3G network. bile subscriber equipment was installed in the baggage compartment of a car. It took nearly ten years to develop NMT, mainly because system designers wanted to make the most of coming finesses in micro- 1956: 0G – the first first MTA system into operation on April 25, electronics: microcircuits, digital frequency 1956, but real system tests had begun two synthesis (to combine radio channels in a ter- networks years earlier, in 1954. During the 1960s, minal), digital signaling, digital switching Enthusiasts at Ericsson and elsewhere had Televerket simultaneously operated two sys- methods (which were necessary for manag- long nurtured the idea of creating a radio- tems. The two were more or less identical ex- ing and controlling telephone switches and based mobile communications system. In the cept for a minor difference in signaling and rapid change-over during handover between mid-1950s, a handful of systems were tested how users connected to the network. cells), and so on. in several countries around the world. For Each system consisted of one transmitter The system was composed of mobile sta- Ericsson’s subsidiary, Svenska Radioaktie- and several receivers and was built using re- tions, base stations, and telephone switch bolaget (SRA), this development was a nat- lays and radio tubes. Four duplex channels equipment. The mobile stations, essentially ural next step – it had been selling private enabled the systems to handle approximately small radio stations with keypads, were often mobile radio systems to the police and other 100 users apiece. The majority of subscribers packaged in a module that could be mount- groups since the 1940s. Now, users would were salaried professionals, such as doctors ed in the cockpit or dashboard of a car. The dial numbers on a telephone to call other or lawyers. The main system shortcomings telephone switches consisted of a subsystem telephones. were limited coverage and subscriber den- (called MTS) of AXE. The base stations What set Ericsson’s system apart from the sity. Ultimately, Televerket concluded that it could thus connect to the switch via ordinary others was that it was fully automatic – it would have to take a radical new approach did not require manual control of any kind. in order to successfully create a national or The system, called MTA, operated in the multinational mobile network. 160MHz band using pulsed signaling be- tween the terminal and base station (MTB, Figure 1 an upgrade introduced in 1965, used dual- tone multifrequency signaling). SRA devel- 1981: 1G – the analog era The mobile unit for MTA, the world’s first automatic mobile telephone system. oped and supplied the base stations and mo- NMT (Nordic Mobile Telephone) was the first bile units (Figure 1). truly mobile system. Ericsson and Televerket Initially, mobile telephony was synony- deployed this open standard in Scandinavia mous with car phones or voice communica- in 1981. At about this same time, Ericsson tion over a mobile radio in a car. It did not also supplied a turnkey system, consisting of matter, therefore, that the equipment was switches, base stations and mobile units, to bulky or heavy. The equipment was also Saudi Arabia. power hungry, because for signals from the Shortly afterward, Bell Labs in the USA mobile unit to reach the base station, the developed what came to be known as AMPS output power from the mobile unit had to (Advanced mobile phone system). The first match that of the base station. AMPS system was deployed in 1984. One The Swedish Telecommunications Admin- other system, TACS (Total access communi- istration (Telia, formerly Televerket) took the cation system, a modification of AMPS), was Ericsson Review No. 3, 2006 101
  • 2. 1991: 2G – transition to digital technology As the 1970s were winding down (and be- fore the analog systems had been taken into operation) the industry foresaw the need for solutions with much greater capacity, paving the way for smaller, more energy-efficient base stations and mobile terminals. In ad- dition, Ericsson foresaw that digital mobile telephony would improve spectrum efficien- cy, compared with analog FM transmission, and allow for the introduction of microcells. New frequencies, two blocks of 25MHz, were reserved in Europe for mobile telephony in the 900MHz band. In 1982, a Scandinavian and Dutch initia- tive in CEPT (European Conference of Postal and Telecommunications Administration) started a Group Speciale Mobile (GSM) to de- fine and specify a pan-European mobile sys- Figure 2 tem for these new frequencies. At the same The size of mobile handsets quickly diminished between 1981 and 1998 thanks to rapid time, Ericsson and Televerket began work- advances in microelectronics and digital tecchnology. In particular, GSM gave rise to ing on the digital system that would become pocket-sized mobile phones. GSM. Ericsson completed its first experi- mental system in 1984. With a 16kbps voice coder, the system proved that digital technol- ogy yielded considerably more capacity than analog systems. The work gave rise to very advanced voice coding, channel coding and telephone lines. And thanks to their modular direction and 25kHz of separation between modulation techniques in 1985. The GSM design, the AXE switches could coordinate adjacent channels. This gave the system a to- group was transferred to ETSI (European mobile and public transit traffic. Initially, tal of 180 channels. Duplex transmission and Telecommunications Standards Institute) the AXE switches were considered to be too reception were separated by 10MHz. when participating operators, manufacturers powerful (and expensive) for mobile systems, Handover and roaming are two techniques and other organizations formed it in 1988. but rapid network growth soon validated at the very heart of mobility. Handover en- GSM was to have digital radio transmis- this design choice. tails passing off calls between base stations. sion and open, clearly defined interfaces, so To provide coverage to large areas, the Roaming entails keeping track of users that operators could select equipment from NMT network was built from a series of when they are not connected so the system different manufacturers. Initially, GSM was cells (a technique developed by Bell Labs) can know where to place a call. Mobile radio intended to be a pan-European mobile net- with one base station per cell. Topography solutions had previously employed DTMF work, but it became a world standard when and the anticipated number of subscribers signaling to manage handover and roam- Telstra (Australia) signed a memorandum of determined the actual number of cells and ing, but Ericsson’s solution (adopted by the understanding in 1992. location of base stations. The base stations industry for the NMT standard) introduced A main theme of Ericsson’s was that GSM associated with a given telephone switch con- digital signaling, which was faster and less would facilitate pocket-sized battery-driven stituted a service area. complex. The system also supported interna- telephones. And, sure enough, GSM was a To prevent interference, neighboring base tional roaming. breakthrough for handheld mobile phones, stations transmitted on separate frequencies. Two versions of the NMT standard were and thus the first global mobile system to One channel in each base station was desig- developed: enjoy really substantial growth (Figure 2). nated a calling channel; the other channels • NMT 450 for the 450MHz frequency As its access technology, GSM combined were used for voice traffic. In small NMT band; and time-division multiple access (TDMA) with base stations, the calling and traffic channels • NMT 900 (in 1986), which used smaller FDMA, which had been used in analog sys- could be combined. A base station’s range de- cells for the 900MHz frequency band. tems. TDMA divides the digitally modu- pended on mast height and topography. The These new frequencies put new technical lated carrier into a number of timeslots for range was often about 20km. requirements on radio network planning. transmitting compressed information. This The system employed duplex channels: one The NMT 900 extension primarily re- approach proved to have several advantages, for transmission (TX) and one for reception sponded to a need for more channels, to including greater traffic capacity, frequency- (RX) with 4.5MHz of bandwidth in each accommodate more subscribers. hopping capability to combat fading, and 102 Ericsson Review No. 3, 2006
  • 3. signal strength measurements made in ter- Ericsson played a decisive role in the minals to facilitate handover. The decision to struggle between TDMA and FDMA for go with TDMA also greatly reduced costs as D-AMPS. There was not any available fre- well as the weight and volume of handsets. quency band in the USA for D-AMPS. In- The next choice, in 1987, was between stead, the digital system would have to be broadband TDMA (2MHz) and narrowband integrated into the existing analog AMPS TDMA (200 to 300kHz). A decisive factor network. Ericsson proposed a TDMA system was that narrowband TDMA facilitated true with a channel width of 30kHz (the same as pocket-sized telephones whereas broadband for analog AMPS). By means of live dem- TDMA would require the terminals to have onstrations of the TDMA solution in Los considerably greater output power, which in Angeles, Ericsson convinced TIA of the sys- turn, would require cooling of some kind tem’s advantages. The first version of TDMA and much larger batteries. shared a control channel with AMPS. How- Ericsson participated in a comprehensive ever, to extend battery life, a digital control field trial in Paris in December 1986, using, channel was introduced in later generations. in contrast to a number of its competitors, The GSM system architecture differed the narrowband TDMA system that later somewhat from that of NMT. It consisted came to serve as the basis for the GSM stan- of a mobile switching system (MSS) with Figure 3 dard (Figure 3). Once the standard was set, mobile switch and home location register Two versions of the first GSM mobile Ericsson had a clear head start over its com- (HLR) and visitor location register (VLR), a phone: prototype and commercial petitors, supplying its first GSM network to base station subsystem (BSS) with groups of handset. Mannesmann (currently Vodafone) in Ger- base stations connected to a base station con- many, in 1991, and handheld mobile phones, troller (BSC), and an operations support sys- also to Mannesmann, in 1992. tem (OSS). And then there were the mobile The GSM system parameters were set as terminals, of course, which were now either weighed several hundred kilograms. But rap- follows: handheld or installed in cars. id advances in technology led to small sta- • 200kHz channel width; and The capacity of the GSM system could be tions that were easy to install and maintain • digital transmission at 22.8kbps – 13kbps increased with smaller cells and more base (Figure 4). Microstations were also developed was to be used for voice and the rest for stations. This quickly led to the allocation for indoor and outdoor usage. These could channel coding. of new frequency bands at 1800MHz and transmit with low power and have a range of In addition, the system would employ slow 1900MHz for small cells. The base stations a few hundred meters (compared with several frequency hops and time multiplexing were initially nearly two meters tall and kilometers for a macrostation). with eight timeslots. Half-rate voice coders were later introduced with close to 8kbps for voice, making it possible to double the Figure 4 number of voice channels over the same Four generations of GSM base stations. bandwidth. Two additional digital systems were devel- Volume and voice channel oped after GSM: 15 • Digital AMPS (D-AMPS, later called TDMA). The system, which was compat- RBS 200 14.8 liter/ ible with AMPS, was first taken into op- voice channel eration in 1992; and 12 • PDC (first called JDC). The system was developed and deployed in Japan in 1993. These systems, which were based on TDMA, 9 had three timeslots but used different chan- nel bandwidths. RBS 2202 At the same time, another standard was 8.1 liter/ being developed in the USA: IS95. This stan- 6 voice channel dard borrowed its radio technology, code- division multiple access (CDMA), from the military. In essence, CDMA differentiates RBS 2206 between users by assigning distinct codes to 3 4.5 liter/ voice channel each. IS95, which used a 1.25MHz carrier, RBS 2216 later became known as narrowband CDMA 2.5 liter/ voice channel (compared with wideband CDMA, which 0 has a 5MHz carrier). 1991 1995 2001 2006 Ericsson Review No. 3, 2006 103
  • 4. From the outset, GSM had been specified Billion subscribers to support international roaming, and as a 2.0 consequence it became a world standard. This, in turn, was a major breakthrough for the pocket-sized handheld telephone. Today, in 2006, GSM has been deployed in more 1.5 than 100 countries and is used by more than two billion subscribers (Figure 5). Moreover, more than 800 million new GSM phones are sold each year. 1.0 Although the first version of GSM was optimized for voice, it could support circuit- switched data transmission at rates of up to 9.6kbps. A modest rate by today’s standards, 0.5 but this was the starting point for mobile data communication and access to the internet. 0 2000: 2.5G – from circuit- 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year switched to packet data GSM continued to evolve, yielding greater Figure 5 capacity and facilitating new services. One GSM and UMTS subscriber growth. method of increasing data transmission rates was to use multiple timeslots in circuit- switched transmissions. With the introduc- tion in 1998 of high-speed circuit-switched data (HSCSD) GSM could offer data trans- mission rates of up to 57kbps. But the real breakthrough came in 2000, with the transition to packet-data technology: Figure 6 general packet radio service (GPRS). This so- Evolution of mobile handsets, size (weight) and talking time. lution reused as much of the circuit-switched 4000 GSM network as possible – frequencies, base stations and BSC – while complementing it with new base station software and two new nodes for packet data: 1000 • a packet-data switch called serving GPRS support node (SGSN), which corresponds 900 to the mobile switch in circuit-switched Talking time [minutes] networks; and 800 Weight [gram] • a gateway GPRS support node (GGSN) for accessing the internet. 700 Ericsson anticipated that IP networks would be used for transport. Accordingly, its mo- 600 bile phones were also designed for internet access. 500 GPRS technology reserves at least one 400 timeslot for packet-data traffic but can use as many as four or five. Therefore, if more 300 timeslots are available, GPRS can yield data transmission rates of up to 100kbps. 200 In 1993, primarily to improve GSM data rates, Ericsson began researching a new 100 modulation method called enhanced data rates for global evolution (EDGE). The regu- 0 lar approach to modulating the radio carrier, 1986 1990 1995 2000 2005 Gaussian minimum-shift keying (GMSK), Year 104 Ericsson Review No. 3, 2006
  • 5. was based on phase and amplitude modula- aging standardization issues and in-house Mobile broadband kbps Long Time Evolution LTE >100Mbps tion using fixed amplitude and two phase product development in parallel, Ericsson 100 000 3G HSPA/MIMO 40Mbps modes, so that each mode corresponded to could save considerable time. 3G HSPA 14Mbps one bit. The new modulation scheme, called • Ericsson opted to base its radio nodes (base 10 000 3G WCDMA 384kbps eight-phase shift keying (8PSK), used eight stations and RNCs) on a new platform EDGE 150kbps modes and three bits per symbol, yielding a (CPP) that was completely packet-based, 1 000 GPRS 100kbps three-fold increase in the bit rate. flexible, and could handle very high data GSM The GSM core network was also updated rates. CPP laid the groundwork for ATM 100 9.6kbps to support multimedia, IP, and streaming and IP transport. Today, CPP serves as a video. Likewise, its interface toward the BSS solid and stable platform for very advanced 10 was modified to serve as the basis for UMTS, 3G products, such as turbo 3G (HSPA), the 3G standard that would constitute the and the future, long-term evolution of 3G 1 1991 2000 2001 2003 2005 2008 20xx next phase of evolution. (LTE). Year WCDMA uses a 5MHz carrier (compared Figure 7 with 200kHz for GSM), which in its first Evolution of mobile data bit rates from 2001: 3G – wideband incarnation, provided data rates of up to GSM to LTE. 384kbps. This is enough to support video coding technology telephony and internet browsing. The The transition to 3G and new technologies broader carrier also eliminates the problem in the mobile network had been driven by of fading (a weakness of narrowband code- user demand for access to the internet and division technology) by distributing interfer- One other complication is time dispersion, data services, such as e-mail and multi- ence throughout the entire band. a phenomenon that arises when signals are media. Networks were thus being optimized WCDMA technology is based on code- reflected on their way to the base station. to deliver packet data instead of for circuit- division techniques (as opposed to frequency Here the solution calls for complex Rake re- switched transmission. division in time) and makes very effective ceivers. The main approach to 3G was wide- use of spectrum. Code-division techniques In addition, optimized signal manage- band (5MHz) code-division multiple access enable a large number of calls to be sent and ment is needed in the base station to reduce (WCDMA) in the 2GHz frequency band. mixed over the same 5MHz channel without power and heat. In hindsight, one can see that WCDMA (the noticeable interference. Each call is differ- Other important pieces of the puzzle in- technology that Ericsson, among others, has entiated by means of a distinct code, which clude a good voice coder and a robust video promoted, and the path selected in Europe the recipient decodes and filters. Moreover, coder that can handle everything from slow to realize 3G) delivers the best performance because all calls are on the same frequency, sequences to rapid exchanges. of any alternative. Simply put, to reach really operators need not plan or optimize network Accordingly, the new WCDMA concept high data rates, one needs a broader carrier. frequency. called for entirely new base station archi- At the same time, EDGE was developed for One technical challenge with CDMA is tecture. Previously, the main focus was on GSM, and in the USA, narrowband cdma- power control. Simply put, signals from mo- channels; that is, the base stations mainly One (1.25MHz) evolved into CDMA2000. bile terminals at different distances from the consisted of several transceivers (transmission As with GSM, Ericsson was first out with base station must all have the same strength and receiver units). By contrast, WCDMA WCDMA, in large part because it had be- at the antenna. The solution is very fast con- employs a function-oriented architecture gun fundamental research on WCDMA even trol algorithms. that manages all processor resources in a before GSM had been taken into operation. In 1995, Ericsson had both a test system and a prototype terminal that was the same size as the GSM prototype had been (Fig- ure 3). In other words, it too could be reduced to a pocket-sized phone. Shortly thereafter, BOX A, A PHONE IN EVERYBODY’S POCKET Ericsson entered into strategic collaboration Two factors have played a decisive role for the success of mobile telephony: the size and price of with NTT DoCoMO in Japan. This led to mobile phones. Ericsson introduced the world’s first pocket-sized mobile phone for NMT 900 in delivery, in 1997, of a pre-commercial system 1987. And during the next ten years it would shrink the size of its mobile phones by 80% (Fig- that would also be used for comprehensive ure 6). Performance, on the other hand, increased one hundred fold, opening the door to a field trials. variety of advanced new services (Figure 7). This evolution is still far from over. The first terminals were telephones with enough intelligence to connect calls, but today’s terminals are actually Two other factors further strengthened powerful handheld computers. Ericsson’s leading position in 3G: • Ericsson initiated a new international fo- Compare the NH 72 (1989) with the Sony Ericsson W850i (2006): rum for 3G, the Third Generation Part- The Ericsson NH 72 was a 420g mobile terminal for NMT voice service. A unique feature in its day enabled users to adjust the volume (loudness) of the handset. The Sony Ericsson W850i nership Project (3GPP), which united Walkman (Figure 8), by contrast, is a 3G terminal that weighs 116g, works on five frequency ETSI in Europe with ARIB in Japan and bands and two systems and supports GPRS, Bluetooth, WAP browsing, e-mail, SMS, MMS, gave the industry a timely push. By man- Java, FM radio, games, music, video, voice memo, a camera, and much, much more. Ericsson Review No. 3, 2006 105
  • 6. WCDMA also requires a transport net- 3G networks. The idea behind HSPA is to work that can deal with variable bandwidth. exploit current radio conditions (in intervals To begin with, asynchronous transfer mode measured in microseconds) for each mobile (ATM) technology was used between the terminal in a given area, by sending data to switch and base station. ATM, a circuit- the mobile terminal that enjoys the best re- switched variable packet link of sorts (that is, ception. Optimum data bit rates are selected a cross between pure circuit-switched tech- using link-adaptation technology. nology and pure packet-data transmission), The objective is to make optimum use gives operators a very flexible and economic of available power by transmitting as much way of transmitting data. Today, however, data with as little power as possible. This most networks are based on or evolving to- way, HSPA supports up to four times more ward an IP paradigm. traffic per cell in the network than the first Ericsson delivered the first WCDMA sys- release of WCDMA. HSPA also considerably tems to 3 in Italy and to J-Phone in Japan. reduces network latency. If GPRS had a de- Ericsson was also first, in 2005, to deliver lay of approximately 1s (early version), then HSPA (the turbo variation of 3G) to Cingu- by comparison, WCDMA would be close to lar in the USA and Vodafone in Japan. 150ms, and HSPA, 70ms. This increase in performance sets users up for a completely new experience, putting mobile broadband Figure 8 Turbo 3G and LTE on par with fixed-line ADSL (at least). The W850i Walkman from Sony Ericsson. The evolution did not end with 3G. High- And the introduction of multiple input, speed 3G or high-speed packet access multiple output (MIMO) antenna technology (HSPA), which is mainly a software upgrade in base stations and mobile phones will bring of WCDMA, further increases radio spec- about further exponential increases in data pool, to enable dynamic bandwidth and al- trum efficiency 200% to 300%. Compared bit rates. Ericsson has already begun testing location of capacity (from only a few kilobits with first-generation WCDMA, HSPA im- MIMO in the field – as usual, long before the per second to 14Mbps depending on service), proves mobile network data rates to a level of technology is ready for commercial use. and to combine circuit-switched data with true broadband. At present (2006), HSDPA The idea is to push HSPA technology to packet data. The capacity of Ericsson’s first delivers 4Mbps and this figure will continue its limits, and tests show that one can reach WCDMA base station was more than three to improve. data bit rates of 40Mbps with 5MHz of radio times that of contemporary GSM base sta- Operators around the world are now rap- bandwidth. At the same time, Ericsson fore- tions. idly installing HSPA technology in their sees an evolution to a 20MHz carrier, which will yield transmission bit rates of up to 200Mbps and flexible use of available band- width. Work on the long-term evolution of 3G (LTE) is already underway (Figure 6). TERMS AND ABBREVIATIONS And as always, Ericsson is conducting early 3GPP Third Generation Partnership GSN GPRS support node system tests to gain first-hand knowledge of Project HLR Home location register this new technology. 8PSK Eight-phase shift keying HSCSD High-speed circuit-switched data Operators and suppliers are currently dis- AMPS Advanced mobile phone system HSPA High-speed packet access cussing the systems, their very high peak ARIB Association of Radio Industries and IP Internet protocol Businesses LTE 3GPP long-term evolution of 3G data rates, and large bandwidths in relevant ATM Asynchronous transfer mode MIMO Multiple input, multiple output standardization bodies. BSC Base station controller MoU Memorandum of understanding Mobile communications have evolved very BSS Base station subsystem MSS Mobile switching system rapidly since the introduction, in 1956, of a CDMA Code-division multiple access NMT Nordic mobile telephone car-borne, walkie-talkie-like mobile system CEPT European Conference of Postal and OSS Operations support system Telecommunications Administration PDC Personal digital communication for a few hundred subscribers. At that time, D-AMPS Digital AMPS (first called JDC) nobody had any idea how fast this concept DTMF Dual-tone multifrequency RNC Radio network controller would catch on or evolve. Even the most EDGE Enhanced data rates for global RX Receiver optimistic predictions fell far short of the evolution SGSN Serving GSN ETSI European Telecommunications SRA Svenska Radioaktiebolaget truth. Standards Institute TACS Total access communication FDMA Frequency-division multiple access system GGSN Gateway GSN TDMA Time-division multiple access GPRS General packet radio service TX Transmitter GMSK Gaussian minimum-shift keying UMTS Universal mobile GSM Group Speciale Mobile telecommunications system GSM Global system for mobile VLR Visitor location register communication WCDMA Wideband CDMA 106 Ericsson Review No. 3, 2006