The US Cell Phone Market
or how I learned to play wacka-mole
Looking to buy a new phone?
- What carrier should I choose?
- What phone should I choose?
- How future proof are these choices?
- Can I switch carriers?
- Will my phone work overseas?
A brief overview
Cell phones have gone through 4 generations numbered 1G through 4G loosely representing the past 4 decades (since 1980).- 1G was the original analog, which used circuit switched networks. This had low-latency (quick response) and connection reliability but very little spectrum efficiency (e.g. downloads were less efficient per MHz). AMPS (Advanced Mobile Phone System)
- 2G added digital downloads and uploads which leveraged packet switched networks. Europe made a concerted effort to standardize radio frequencies and protocols via GSM (Global System for Mobile Communications), while most of the US carriers went their own ways. Common GSM protocol names were GRPS (General Packet Radio Service) and EDGE (Enhanced Data Rates for GSM Evolution).
- 3G started in 2000 in Europe as a general specification UMTS (Universal Mobile Telecommunications System) which stated 3G will be anything that is 200kbps or faster and must be all digital. This included HSPA (High Speed Packet Access), later faster downloads with HSDPA (High Speed Downlink Packet Access). Still later HSUPA (High Speed Uplink Packet Access). And finally HSPA+ (with between 5Mbps to 48Mbps). A major competing standard was CDMA2000 which included 1xRTT and EV-DO (Evolution-Data only later rebranded as Evolution-Data Optimized). And finally WiMAX (Worldwide Interoperability for Microwave Access).
- 4G was guided by IMT Advanced (International Mobile Telecommunications-Advanced) in 2008 to define the most recent generation. This included a minimum bandwidth of 1Gbps, and a requirement to be pure IP based. It basically leveraged OFDM (Orthogonal frequency-division multiplexing)- a technique leveraged in short-range WiFi since 802.11a. It also leveraged the latest WiFi techniques (802.11n) of multi-antenna / multi-path, often called MIMO (multiple-input and multiple-output). However, there were major challenges, given existing radio frequency spectrum allocations, costs, and handset requirements. So a practical evolutionary approach was decided on called LTE (Long Term Evolution) and subsequently LTE Advanced. Separately higher speed WiMAX solutions have been adopted by some vendors. LTE peek speeds are currently on the order of 50Mbps. Far short of the 4G requirement. More importantly, there is tremendous overlap of LTE and HSPA+ deployments.
The basic problem
Radio frequencies have the following characteristics:- A Frequency is measured in HZ (after Heinrich Hertz), and it represents one full rotation (similar to a rotating tire - but more specifically a complete sinusoidal oscillation between two orthogonal states).
- Radio frequencies are split up in a continuous spectrum much like color shades from red through violet (as can be seen through a prism).
- This means there are a very large number of frequencies between even 1HZ and 2HZ (though quantum physics quickly gets in the way).
- Radio Frequencies are categorized as those between 3Hz and 300GHz.
- The frequencies commonly attributed to Cell phones are UHF (Ultra High Frequency) 300MHz - 3GHz.
- What is interesting about Radio Frequencies is that they can emit off copper wires and be captured again by a different copper wire miles away.
- Some radio frequencies can pass through walls, while others have a hard-time. Still others' are subject to natural interference.
- For a given power level, some frequencies can travel great distances with little signal loss; others can only travel a few inches. For those shorter range frequencies, you can usually increase the power of the transmitter to increase the range, but sometimes there are consequences - an Arc-welder, for example, is a high powered radio transmitter.
- Radio transmissions are composed of oscillating multi-dimensional bundles of energy called photons that continuously transition back and forth between the electric and magnetic fields, while simultaneously traveling through space at the speed of light.
- The process of transmitting radio frequencies wirelessly through space is very similar to how they are transmitted through a waveguide such as a copper wire.
- As a consequence, wired ethernet and fiber-optics have very similar limitations as wireless - but have the advantage that multiple parallel cables have very little interference with one another - So you can achieve massive bandwidth with very little power consumption.
- Antenna's are basically echo-chambers that can absorb 50% of the power in a given radio photon. The remaining 50% is echo'd/reflected back out.
- This means radio transmission is never more than 50% power efficient
- Given a long-lasting coherent frequency, the echo's resonate within the antenna's echo-chamber and can coherently be amplified (in the case of analog music radios like FM/AM) or measured / sampled (in digital systems).
- Minor obstructions in the wires of an antenna have massive effects on which frequencies the echo chamber can resonate effectively. This is more-or-less how we can tune a wire to accept ONLY a small frequency-range.
- We call a pre-defined frequency-range a channel (VHF channel 13 is 156.65 MHz +/- 25 KHz)
- A GSM cell tower may define 124 channels centered about 850MHz in 200 KHz increments.
- There is bleeding of one frequency into the next due to noise, photon-scattering (e.g. through air), and the basic physics involved in antennas. So while a given photon is precisely 1 frequency (for example 30,153.112212 Hz), the resonation-amplified signal will not be determinable beyond an accuracy of say 5kHz at the 30Mhz level. Thus an entire contiguous band needs to be allocated/reserved.
- Using mathematical techniques on digitally sampled measurements of the antenna, we can effectively encode between 0.1 and 20 bits per Hz of a given contiguous frequency-band.
- Thus if a cell phone was allocated a 1 MHz band somewhere in the UHF range of 300MHz to 3GHz, then they may be able to encode between 100Kbps and 20Mbps. Note, there would only be 2,700 such bands in the UHF range. So for a given region, you could not support more than 2,700 cell phones with such a partitioning scheme.
- The measurement of bits per preciously scarce Hz is called spectral efficiency.
- Given the ever increasing cost of frequency-ranges in given geographic regions (such as high population areas), there is an ever growing need to increase spectral efficiency - all else being equal.
- When you sell a device that uses a frequency, you have to wait until they have all been retired before you can effectively re-purpose that frequency for a different device or protocol.
- Thus, historically the frequency spectrum is full of ranges that you are not allowed to use because of spectrum squatters.
- In the US, the FCC (Federal Communications Commission) defines what devices are allowed to use which frequency-ranges; what protocols to use in those ranges, and at what max-power-levels (so as to define a max-range/distance of interference)
- You can generally separate two-way send/recieves in frequency or time (or some combination there-of).
- TDMA - Time Division Multiple Access
- FDMA - Frequency Division Multiple Access
- CDMA - Code Division Multiple Access (combines a range of frequencies over time to produce a code-point that
Today that market is the cellphone industry.
BUT, much of that spectrum is already allocated for cell-phone use. And there are over 1 billion cell phone devices world-wide. There is a very high cost in upgrading older cell phone devices that have less spectral efficiency or to consolidate which frequencies are used for which protocols, so a given phone can be useful in different cities around the world. So instead, most carriers will opt to continue to fragment the world-wide-market for short-term cost-savings.
So lets say we have 2 cities A and B that each implemented their own 3G phone Phone 1 and Phone 2. Lets say they used frequencies 1 GHz and 2 GHz respectively. Lets say there was some legacy satalite blocking 1 GHz in city B.
Now lets say they both wanted to create a 4G network. Let's say in City A, the only available frequency is 3 GHz. So they create a Phone 3 (that is backwardly compatible with Phone 1's frequencies) . But in City B, it was cheaper to decommision that satalite and reuse the 1 GHz space. Lets also say 3 GHz is NOT currently cost effective to re-purpose. So City B KNOWs that if it chooses 1 GHz it will be in conflict with City A. But it would take many years and a lot of money to do something else - so instead they create a Phone 4. So now Phone 1 and 3 work in City A ONLY, and Phones 2 and 4 ONLY work in City B.
Now take this situation and take 20 frequencies and 15 protocols. Many of which requires special dedicated hardware to work properly. Depending on the details, there could be upwards of 100 specialized pieces of hardware required to actually work on all possible frequencies and protocols. While technically possible, the cost-effectiveness of making a LOW-POWER portable cell phone is perhaps challenging. Now throw in patents / royalties for a given protocol, and a handset manufacturer has to think seriously about whether it's worth while making a true world phone (one that can operate in any major city around the world with at least voice connectivity).
The breakdown
Europe:
While Europe is full of conflicting standards, it did champion the GSM standard. This allocated the following frequencies:
While Europe is full of conflicting standards, it did champion the GSM standard. This allocated the following frequencies:
- 900MHz (890-915 uplink, 935-960 downlink) GSM / EDGE / GRPS/ 2G with 124 channel-pairs.
- 1.8GHz (1.710-1.785 uplink, 1.805-1.880 downlink) GSM / EDGE / GRPS/ 2G with 374 channel-pairs.
- 1.9GHz / 2.1GHz IMT (1920–1980 uplink, 2110–2170 downlink) UMTS / 3G / W-CDMA (2004 - )
- 1.8GHz DCS (1710–1785 uplink, 1805–1880 downlink) UMTS / 3G / W-CDMA (alternative / migration)
- 900GHz GSM (880-915 uplink, 925-960 downlink) UMTS / 3G / W-CDMA (alternative / migration)
US:
Due to conflicts, the US allocated these (and other) frequencies:
- 800MHz (825 - 894) for 1G AMPS (FDMA) then incrementally upgraded to 2G D-AMPS (TDMA) in ATT / Verizon / On-Star (started in 1982 and discontinued in 2008).
- 850MHz (824-849 uplink, 869-894 downlink) GSM / EDGE / GRPS/ 2G with 124 channel-pairs.
- 850MHz T-Mobile for GSM (1996-) ROAMING ONLY
- 850MHz (824-849 uplink 869-894 downlink) ATT UMTS / HSPA / 3G (HSDPA 2005 ) (HSUPA in 2009 ) - slowly replacing GSM
- 850MHz Verizon CDMA / 3G
- 1.9GHz Verizon CDMA / 3G
- 1.9GHz T-Mobile GSM / 2G (1994-) (GPRS 2002) (EDGE 2004)
- 1.9GHz ATT GSM / 2G (GPRS 2002 ) (EDGE 2004 )
- 1.9GHz (1.85-1.99) Sprint 2G CDMA / GSM custom.(1995 - 2000)
- 1.9GHz PCS Sprint CDMA / EV-DO
- 1.7GHz / 2.1GHz AWS (1.71-1.755 uplink, 2.11-2.155 downlink) T-Mobile UMTS / 3G (W-CDMA 3.6Mbps in 2006) (HSPA 7.2Mbps in 2010) (HSPA+ 42Mbps in 2011)
- 1.9GHz PCS (1.85-1.91 uplink 1.93-1.99 downlink) ATT UMTS / HSPA / 3G (HSDPA 2005) (HSUPA in 2009) - slowly replacing GSM
- 700MHz ATT LTE / 4G (2011 - )
- 700MHz (777-787 uplink, 746-756 downlink) Verizon UMTS / 3G
- 2.5-2.7GHz Sprint XOMH WiMAX / 4G
- AMPS (0.03 bits/Hz)
- D-AMPS (1.62 bits/Hz) Each channel-pair is 30KHz wide in 3 time slots (TDMA). Supports 94 channel-pairs.
- GSM Each channel is 200KHz wide.
- GSM / GPRS (?? ) ( 56Kbps to 154Kbps)
- GSM / EDGE (1.92 bits/Hz) (400Kbps to 1Mbps)
- CDMA2000 / EV-DO (2.5 bits/Hz) (2.4Mbps to 3.1Mbps) 1.25MHz
- UMTS / WCDMA / HSDPA (8.4 bits/Hz) (1.4Mbps to 14Mbps) 5MHz channel-pairs
- UMTS / HSPA+ (42Mbps)
- LTE Advanced (16 bits/Hz) (6Mbps normal peek 300Mbps) 1.25MHz .. 20 MHz channel-bundles
- WiMAX (1.75 to 20 bits/Hz)
- V.92 modem (18.1 bits/Hz)
- 802.11g (20 bits/Hz)
- 802.11n (20 bits/Hz)
- Apple's iPhone 4 contains a quadband chipset operating on 850/900/1900/2100 MHz, allowing usage in the majority of countries where UMTS-FDD is deployed. Note, this doesn't support the 1.7GHz uplink for T-Mobile.
- Samsung Galaxy S Vibrant (SGH-T959) T-Mobile - GSM / 2G 850, 900, 1800, and 1900. UMTS 1700/2100 (US, Tmobile only) and UMTS 1900/2100 (Europe). It does NOT support the 850 band as used by AT&T 3G.
- Samsung Galaxy S Captivate (SGH-i897) ATT -GSM / 2G 850, 900, 1800 and 1900. UMTS / 3G 850/1900 (US, ATT) and UMTS / 3G 1900/2100 (Europe).
- Samsung Galaxy S II (SGH-I777) ATT - GSM/3G 850/1900 (US) 900/1800 (Europe)
UMTS / 3G 850/1900 (US, ATT) and UMTS / 3G 1900/2100 (Europe) [1.2 GHz, Dual Core Exnyos C210 + Mali-400 MP GPU] - Samsung Galaxy S II (SGH-T989) T-Mobile - HSPA+ [1.5 GHz, Dual Core Qualcomm Snapdragon S3]
- Samsung Galaxy S II Skyrocket (SGH-I727) ATT - HSDPA / 3G 850 / 1900 / LTE 700MHz [1.5 GHz dual-core Snapdragon S3]
The VAST majority of the data was garnered from wikipedia and general google searches. If I come across more detailed information in my spare time, I'd love to update the data.
References:
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