The Future 4G

So what's next? The standards bodies are back at work defining the fourth generation of wireless network protocols, sometimes termed LTE (for Long Term Evolution). The apparent winner is a group of protocols called Orthogonal Frequency Division Multiplexing (OFDM), or sometimes OFDMA (the "A" is for Access). These protocols use

* Except for operators in the People's Republic of China, where the government mandated its own version of UMTS, called Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). TD-SCDMA uses TDMA as well as CDMA to provide some unique advantages for data traffic. It also avoids the need for PRC handset makers to pay royalties for most WCDMA intellectual property.

radio frequency subcarriers to further improve the data rates achievable for wireless devices. Similar protocols are used in the WiMAX standards (the higher bandwidth, longer-range follow-on to WiFi), but it is not clear how WiMAX and LTE will relate to one another.

Just as with 3G, a round of spectrum auctions is starting to take place for 4G, and operators are already investing large sums of money into getting ready for 4G services. Suffice to say that your applications built for Android will someday encounter phones running 4G protocols, and will be able to take advantage of the higher data rates and lower latencies that will come with these protocols.

To wrap up, Figure A-1 shows the evolution of protocols discussed in this chapter in relation to the decade in which they were first deployed and the effective bandwidth they achieve.


WiMAX (up to 75Mb) TD-SCDMA (up to 2MB) |


WCDMA/HSPA (up to 10Mb)

1 «

CDMA/EV-DO (400Kb-2Mb) GSM/Edge (up to 474Kb)



CDMA/lxRTT (up to 144Kb)

& es

1995 1990

GSM/GPRS (up to 114Kb) HSCSD (24.2Kb-64Kb)

10Kb/s 100Kb/s 1M/s 10M/s 100M/s

Theoretical speed range (log scale)

Figure A-1. Mobile protocols, bandwidth, and dates of deployment

Figure A-1. Mobile protocols, bandwidth, and dates of deployment

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