Posts Tagged ‘CDMA’
Have you ever been confused the over abundance of acronyms used by cell providers to describe their phones and plans? If you’ve been confused by terms like 2G, 3G, CDMA, GSM, HSPA, or even 2.5G… Then this is the article for you.
2G - 2G refers to the second generation of networks, namely CDMA and GSM/GPRS. 2G networks and phone transmit in digital (instead of analog as used in 1G).
GSM – GSM is the most widely used cell phone standard in the world, and used by AT&T and T-Mobile in the US.
- GSM phones use a SIM card to identify you to the phone network (it’s short for “Subscribed Identification Module”).
- By swapping this card between phones, you can easily switch your active cell phone.
- Non-GSM networks, like Verizon and Sprint, require you to call customer service when switching phones.
- Some GSM phones ship in a “locked” state which only allows the phone to work with one carrier.
- This is often done in countries where the cell providers subsidize the phones in exchange for customers entering contracts with them. By SIM locking the phone, they make it difficult for customers to switch to another network.
- The iPhone in the US (and other countries) is a well known example of a SIM locked phone. While technically, the phone’s radio could work on T-Mobile’s voice network, it’s “SIM Locked” to AT&T. Therefore, an AT&T SIM card is needed in order to make or receive calls.
- There are various methods of removing the SIM locked placed on a phone.
- In some cases, the cell provider will actually provide an unlock code. However, this is usually not given out until a refund period has passed. This prohibits people from purchasing a phone with the sole intent to unlock it for use on another network.
- If the provider will not give out unlock codes (as with the iPhone), sometimes there are software or hardware “hacks” that can be performed to unlock it.
- While a hacked unlock phone can be used on other networks, installing software updates often re-enables the SIM Lock. Requiring the phone to be re-hacked.
- Sometimes, it’s possible to by-pass the SIM lock on a particular phone model by simply purchasing the phone from a country where it is shipped in an unlocked state. For example, iPhones in Australia are sold without a SIM lock (sometimes referred to as ‘Factory Unlocked’). One purchased there can be used on any GSM carrier, including T-Mobile in the US.
- GSM works on four separate frequencies: 850, 900, 1800 and 1900.
- GSM phones are sometimes advertised as “dual band” or “quad band” to describe the number of frequencies they use.
- In the US and Canada, GSM phones use the 850 & 1900 bands.
- In Europe, the Middle-East, Asia and Australia, they typically use the 900 & 1800 bands.
- Quad-Band GSM phones are particularly useful for international travel as you can be assured that it will work with the local providers frequencies (provided that they use GSM – see below for the exceptions).
CDMA - CDMA (Code Division Multiple Access) is a competing digital cell phone standard.
- It is only used in a few markets: Japan, South America, Korea and the US on Verizon & Sprint.
- CDMA is more efficient in its use of bandwidth. However, it lacks the worldwide market-share and SIM card swap-ability that GSM phones offer.
2.5G - 2.5G is use to refer to data networks that are faster than the original 2G offerings, but are not technically 3G.
- The GSM 2.5G data network is called “edge” and can be found on AT&T and T-Mobile.
- The CDMA 2.5G data network is called 1xRTT.
3G – 3G includes wide-area wireless voice, and higher speed wireless data. 3G is the first wireless network that offers DSL like speeds on mobile devices (1.75MBs). In the US, 3G data has two standards, one for GSM, and one for CDMA. For GSM the standard is called HSPA; on AT&T and T-Mobile. For CDMA the standard is EV-DO; on Verizon and Sprint.
- HSPA – HSPA stands for High Speed Packet Access and is the 3G data communication standard used by GSM providers.
- HSPA encompasses additional standards called HSDPA and HSUPA.
- Depending on which study you choose to believe, HSPA averages around 2MBs speeds.
- T-Mobile is rolling out a version of HSDPA called HSPA+ which promises a 21Mbps speed. It’s currently being rolled out in the US, but as of July 1st, 2010, it’s only available in a few cities.
- EV-DO – EV-DO stands for Evolution Data Optimized and is the 3G data communication standard used by CDMA providers.
- Verizon and Sprint both offer EV-DO Data Plans in the US.
- Like HSPA, there are many different revision of the specification; namely Rev 0 (with speeds around 150 Kbps) , Rev A (with speeds around 3.1Mbos) and Rev B (with speeds around 14.7Mbps).
4G – 4G is where the real excitement about wireless data exists. It promises download speeds equal or faster than home broadband. Like other wireless data technologies, it comes in two standards: LTE and WiMax.
- WiMax – WiMax is and extreme-high-speed wireless data technology being deployed nationwide by Sprint.
- The current Wimax revision provide speeds up to 128MBps (although no current devices support that speed yet.)
- The first HTC Evo 4G started shipping on June 4, 2010 making it the first 4G.WiMax Device available in the US.
- LTE – LTE stands for Long Term Evolution, and offers top theoretical speeds of 100 Mbps.
- It’s a GSM based technology and appears to be the dominant next-gen standard, as both Verizon and AT&T plan to roll out LTE in the future.
- Since Verizon’s network is currently based on CDMA, they will roll out LTE in addition to their existing network (so they will be supporting two technologies until all customers eventually migrate to LTE based phones.)