Comparison of mobile phone standards

A comparison of mobile phone standards can be done in many ways.

Issues

Global System for Mobile Communications (GSM, around 80–85 % market share) and IS-95 (around 10–15 % market share) were the two most prevalent 2G mobile communication technologies in 2007.^[1] In 3G, the most prevalent technology was UMTS with CDMA-2000 in close contention.

All radio access technologies have to solve the same problems: to divide the finite RF spectrum among multiple users as efficiently as possible. GSM uses TDMA and FDMA for user and cell separation. UMTS, IS-95 and CDMA-2000 use CDMA. WIMAX and LTE use OFDM.

• Time-division multiple access (TDMA) provides multiuser access by chopping up the channel into sequential time slices. Each user of the channel takes turns to transmit and receive signals. In reality, only one person is actually using the channel at a specific moment. This is analogous to time-sharing on a large computer server.

• Frequency-division multiple access (FDMA) provides multiuser access by separating the used frequencies. This is used in GSM to separate cells, which then use TDMA to separate users within the cell.

• Code-division multiple access (CDMA) This uses a digital modulation called spread spectrum which spreads the voice data over a very wide channel in pseudorandom fashion using a user or cell specific pseudorandom code. The receiver undoes the randomization to collect the bits together and produce the original data. As the codes are pseudorandom and selected in such a way as to cause minimal interference to one another, multiple users can talk at the same time and multiple cells can share the same frequency. This causes an added signal noise forcing all users to use more power, which in exchange decreases cell range and battery life.

• OFDM uses bundling of multiple small frequency bands that are orthogonal to one another to provide for separation of users. The users are multiplexed in the frequency domain by allocating specific sub-bands to individual users. This is often enhanced by also performing TDMA and changing the allocation periodically so that different users get different sub-bands at different times.

In theory, CDMA, TDMA and FDMA have exactly the same spectral efficiency but practically, each has its own challenges – power control in the case of CDMA, timing in the case of TDMA, and frequency generation/filtering in the case of FDMA.

For a classic example for understanding the fundamental difference of TDMA and CDMA imagine a cocktail party, where couples are talking to each other in a single room. The room represents the available bandwidth:

TDMA: A speaker takes turns talking to a listener. The speaker talks for a short time and then stops to let another couple talk. There is never more than one speaker talking in the room, no one has to worry about two conversations mixing. The drawback is that it limits the practical number of discussions in the room (bandwidth wise).

CDMA: any speaker can talk at any time; however each uses a different language. Each listener can only understand the language of their partner. As more and more couples talk, the background noise (representing the noise floor) gets louder, but because of the difference in languages, conversations do not mix. The drawback is that at some point, one cannot talk any louder. After this if the noise still rises (more people join the party/cell) the listener cannot make out what the talker is talking about without coming closer to the talker. In effect, CDMA cell coverage decreases as the number of active users increases. This is called cell breathing.

Comparison table

Feature	NMT	GSM	UMTS (3GSM)	IS-95 (CDMA one)	IS-2000 (CDMA 2000)
Technology	FDMA	TDMA and FDMA	W-CDMA	CDMA	CDMA
Generation	1G	2G	3G	2G	3G
Encoding	Analog	Digital	Digital	Digital	Digital
Year of First Use	1981	1991	2001	1995	2000 / 2002
Global market share	0%	72%	12%	0.6%	12%
Roaming	Nordics and several other European countries	Worldwide, all countries except Japan and South Korea	Worldwide	Limited	Limited
Handset interoperability	None	SIM card	SIM card	None	RUIM (rarely used)
Operator locking	Monopoly	Unlockable	Unlockable	ESN	ESN
Common Interference	None	Some electronics, e.g. amplifiers	None	None	None
Signal quality/coverage area	Good coverage due to low frequencies	Good coverage indoors on 850/900 MHz. Repeaters possible. 35 km hard limit.	Smaller cells and lower indoors coverage on 2100 MHz; equivalent coverage indoors and superior range to GSM on 850/900 MHz.	Unlimited cell size, low transmitter power permits large cells	Unlimited cell size, low transmitter power permits large cells
Frequency utilization/Call density	Very low density	0.2 MHz = 8 timeslots. Each timeslot can hold up to 2 calls (4 calls with VAMOS) through interleaving.	5 MHz = 2 Mbit/s. 42Mbit/s for HSPA+. Each call uses 1.8-12 kbit/s depending on chosen quality and audio complexity.	Lower than CDMA-2000?	1.228  MHz = 3Mbit/s
Battery life	Low, due to high transmitter power (1 watt)	Very good due to simple protocol, good coverage and mature, power-efficient chipsets.	Originally lower than GSM, but with new chipsets, DTX/DRX and Voice over HSPA all improve battery life close to that of GSM.	Lower due to high demands of CDMA power control.	Lower due to high demands of CDMA power control and young chipsets.
Handoff	Hard	Hard	Soft	Soft	Soft
Cell Breathing	No	No	Yes	Yes	Yes
Voice and Data at the same time	No	Yes GPRS Class A	Yes[2]	No	Yes SVDO[3]
Intellectual property	Scandinavian telecom operators	Concentrated among a few manufacturers	Concentrated among a few manufacturers	Qualcomm	Qualcomm

Traceability comparison

Strengths and Weaknesses of IS-95 and GSM^[4]

Advantages of GSM

• GSM is mature; this maturity means a more stable network with robust features.
• Less signal deterioration inside buildings.
• Ability to use repeaters.
• Talktime is generally higher in GSM phones due to the pulse nature of transmission.
• The availability of Subscriber Identity Modules allows users to switch networks and handsets at will, aside from a subsidy lock.
• GSM covers virtually all parts of the world so international roaming is not a problem.
• The much bigger number of subscribers globally creates a better network effect for GSM handset makers, carriers and end users.

Disadvantages of GSM

• Interferes with some electronics, especially certain audio amplifiers.
• Intellectual property is concentrated among a few industry participants, creating barriers to entry for new entrants and limiting competition among phone manufacturers. Situation is however worse in CDMA-based systems like IS-95, where Qualcomm is the major IP holder.^{[citation needed]}
• GSM has a fixed maximum cell site range of 120 km,^[5] which is imposed by technical limitations.^[6] This is expanded from the old limit of 35 km.

Advantages of IS-95

• Capacity is IS-95's biggest asset; it can accommodate more users per MHz of bandwidth than any other technology.
• Has no built-in limit to the number of concurrent users.
• Uses precise clocks that do not limit the distance a tower can cover.^[7]
• Consumes less power and covers large areas so cell size in IS-95 is larger.
• Able to produce a reasonable call with lower signal (cell phone reception) levels.
• Uses soft handoff, reducing the likelihood of dropped calls.
• IS-95's variable rate voice coders reduce the rate being transmitted when speaker is not talking, which allows the channel to be packed more efficiently.
• Has a well-defined path to higher data rates.

Disadvantages of IS-95

• Most technologies are patented and must be licensed from Qualcomm.
• Breathing of base stations, where coverage area shrinks under load. As the number of subscribers using a particular site goes up, the range of that site goes down.
• Because IS-95 towers interfere with each other, they are normally installed on much shorter towers. Because of this, IS-95 may not perform well in hilly terrain.
• IS-95 covers a smaller portion of the world, and IS-95 phones are generally unable to roam internationally.
• Manufacturers are often hesitant to release IS-95 devices due to the smaller market, so features are sometimes late in coming to IS-95 devices.
• Even barring subsidy locks, CDMA phones are linked by ESN to a specific network, thus phones are typically not portable across providers.

Development of the Market Share of Mobile Standards

This graphic compares the market shares of the different mobile standards.

Cellphone subscribers by technology (left Y axis) and total number of subscribers globally (right Y axis)

In a fast growing market, GSM/3GSM (red) grows faster than the market and is gaining market share, the CDMA family (blue) grows at about the same rate as the market, while other technologies (grey) are being phased out.

Comparison of wireless Internet standards

As a reference, a comparison of mobile and non-mobile wireless Internet standards follows.

Comparison of Mobile Internet Access methods (This box: view · talk · edit)

Common Name	Family	Primary Use	Radio Tech	Downstream (Mbit/s)	Upstream (Mbit/s)	Notes
HSPA+	3GPP	Used in 4G	CDMA/FDD MIMO	21 42 84 672	5.8 11.5 22 168	HSPA+ is widely deployed. Revision 11 of the 3GPP states that HSPA+ is expected to have a throughput capacity of 672 Mbps.
LTE	3GPP	General 4G	OFDMA/MIMO/SC-FDMA	100 Cat3 150 Cat4 300 Cat5 (in 20 MHz FDD) [8]	50 Cat3/4 75 Cat5 (in 20 MHz FDD)[8]	LTE-Advanced update expected to offer peak rates up to 1 Gbit/s fixed speeds and 100 Mb/s to mobile users.
WiMAX	802.16	Mobile Internet cf. 802.16e	MIMO-SOFDMA	128 (in 20 MHz bandwidth FDD)	56 (in 20 MHz bandwidth FDD)	WiMAX update IEEE 802.16m is to offer peak rates of at least 1 Gbit/s fixed speeds and 100 Mbit/s to mobile users.[9]
Flash-OFDM	Flash-OFDM	Mobile Internet mobility up to 200 mph (350 km/h)	Flash-OFDM	5.3 10.6 15.9	1.8 3.6 5.4	Mobile range 30 km (18 miles) extended range 55 km (34 miles)
HIPERMAN	HIPERMAN	Mobile Internet	OFDM	56.9
Wi-Fi	802.11 (11n)	Mobile Internet	OFDM/MIMO	300 (using 4x4 configuration in 20 MHz bandwidth) or 600 (using 4x4 configuration in 40 MHz bandwidth)		Antenna, RF front end enhancements and minor protocol timer tweaks have helped deploy long range P2P networks compromising on radial coverage, throughput and/or spectra efficiency (310 km & 382 km)
iBurst	802.20	Mobile Internet	HC-SDMA/TDD/MIMO	95	36	Cell Radius: 3–12 km Speed: 250 km/h Spectral Efficiency: 13 bits/s/Hz/cell Spectrum Reuse Factor: "1"
EDGE Evolution	GSM	Mobile Internet	TDMA/FDD	1.6	0.5	3GPP Release 7
UMTS W-CDMA HSDPA+HSUPA	UMTS/3GSM	General 3G	CDMA/FDD CDMA/FDD/MIMO	0.384 14.4	0.384 5.76	HSDPA is widely deployed. Typical downlink rates today 2 Mbit/s, ~200 kbit/s uplink; HSPA+ downlink up to 56 Mbit/s.
UMTS-TDD	UMTS/3GSM	Mobile Internet	CDMA/TDD	16		Reported speeds according to IPWireless using 16QAM modulation similar to HSDPA+HSUPA
EV-DO Rel. 0 EV-DO Rev.A EV-DO Rev.B	CDMA2000	Mobile Internet	CDMA/FDD	2.45 3.1 4.9xN	0.15 1.8 1.8xN	Rev B note: N is the number of 1.25 MHz chunks of spectrum used. EV-DO is not designed for voice, and requires a fallback to 1xRTT when a voice call is placed or received.

Notes: All speeds are theoretical maximums and will vary by a number of factors, including the use of external antennae, distance from the tower and the ground speed (e.g. communications on a train may be poorer than when standing still). Usually the bandwidth is shared between several terminals. The performance of each technology is determined by a number of constraints, including the spectral efficiency of the technology, the cell sizes used, and the amount of spectrum available. For more information, see Comparison of wireless data standards.

For more comparison tables, see bit rate progress trends, comparison of mobile phone standards, spectral efficiency comparison table and OFDM system comparison table.

See also

• Comparison of wireless data standards
• Spectral efficiency comparison table
• SMS - contain the content of its standardization

References

1. ^ "Subscriber statistics end Q1 2007". Archived from the original on 2007-09-27. http://web.archive.org/web/20070927162249/http://www.gsmworld.com/news/statistics/pdf/gsma_stats_q1_07.pdf. Retrieved 2007-09-22. 
2. ^ UMTS/HSPA (3G) Mobile Broadband - Wireless from AT&T
3. ^ CDMA Development Group Announces 'SVDO': Handle Calls and Data at same time
4. ^ "IS-95 (CDMA) and GSM(TDMA)". http://zone.ni.com/devzone/cda/tut/p/id/7107. Retrieved 2011-02-03. 
5. ^ http://www.allbusiness.com/electronics/computer-electronics-manufacturing/6838169-1.html
6. ^ http://www.arcx.com/sites/faq.htm
7. ^ Frequently Asked PCS Questions
8. ^ ^{a b} "LTE". 3GPP web site. 2009. http://www.3gpp.org/article/lte. Retrieved August 20, 2011. 
9. ^ "UQ (Japan) WiMAX 2 field trial". http://www.uqwimax.jp/english/news_release/201107061.html. Retrieved July 6, 2011.