*Another technology/technique involved in 4G communications
MIMO (Multiple Input/Multiple Output): MIMO is a wireless technology that employs multiple intelligent input and output radio antennas to improve transmission speed and quality over longer distances than otherwise possible. The technique involves Space Division Multiplexing (SDM), with arrays of multiple spatially separated transmit and receive antennas. The idea is to push 802.11 (also known as Wi-Fi) WLAN (Wireless Local Area Network) transmission rates from around 20 Mbps to at least 100 Mbps and perhaps as high as 540 Mbps. MIMO also will extend 802.11 distances from 100 meters to as much as 200 meters. MIMO is the basis for the developing IEEE 802.11n standard and promotes spectral efficiency during 4G communications. MIMO is typically combined with OFDM (Orthogonoal Frequency-Division Multiplexing) to achieve an even greater level of spectral efficiency.
Monday, July 13, 2009
Thursday, July 9, 2009
OFDM (Orthogonal Frequency Division Multiplexing) **4G technology**
In the next few WotD’s we’ll take a look at the principal technologies that comprise 4G…
OFDM (Orthogonal Frequency Division Multiplexing): A modulation technique for wireless communications, OFDM was patented by Bell Labs in 1970, and initially was used in a naval communications system dubbed ‘Catherine’. Much like DMT (Discrete MultiTone), OFDM splits the datastream into multiple RF (Radio Frequency) channels, each of which is sent over a subcarrier frequency. DMT and other more conventional techniques encode data symbols for a given data stream onto one radio frequency. In an OFDM system, however, each tone (i.e., frequency) is orthogonal (i.e., independent or unrelated) to the other tones; multiple data symbols are encoded concurrently onto multiple tones in a parallel fashion. The signal-to-noise ratio of each of those very precisely defined frequencies is carefully monitored to ensure maximum performance. OFDM eliminates the requirement for guard bands to separate the frequencies and, thereby, avoid interference from adjacent RF channels. Guard bands are required only around the edges of a set of tones, i.e., RF channels. This yields greater spectral efficiency, as virtually all of the allocated RF spectrum can be used for data transmission.
OFDM is used by the HomePlug Powerline alliance to avoid line noise in a residential power-line network. How it works:
1. Broadband content from cable modem, DSL or satellite is fed to home gateway
2. By plugging gateway into any electrical outlet, content is bridged to any HomePlug-enabled device
3. OFDM takes multiple signals of different frequencies and combines them to form one signal to avoid line “noise”
4. HomePlug network monitors power lines for “noise”.
For more on HomePlug visit their website: http://www.homeplug.org/home
If noise occurs on a particular frequency, OFDM engine shifts transmission to another frequency. OFDM also is used in the IEEE 802.16 WLL specification, also known as WiMax.
OFDM (Orthogonal Frequency Division Multiplexing): A modulation technique for wireless communications, OFDM was patented by Bell Labs in 1970, and initially was used in a naval communications system dubbed ‘Catherine’. Much like DMT (Discrete MultiTone), OFDM splits the datastream into multiple RF (Radio Frequency) channels, each of which is sent over a subcarrier frequency. DMT and other more conventional techniques encode data symbols for a given data stream onto one radio frequency. In an OFDM system, however, each tone (i.e., frequency) is orthogonal (i.e., independent or unrelated) to the other tones; multiple data symbols are encoded concurrently onto multiple tones in a parallel fashion. The signal-to-noise ratio of each of those very precisely defined frequencies is carefully monitored to ensure maximum performance. OFDM eliminates the requirement for guard bands to separate the frequencies and, thereby, avoid interference from adjacent RF channels. Guard bands are required only around the edges of a set of tones, i.e., RF channels. This yields greater spectral efficiency, as virtually all of the allocated RF spectrum can be used for data transmission.
OFDM is used by the HomePlug Powerline alliance to avoid line noise in a residential power-line network. How it works:
1. Broadband content from cable modem, DSL or satellite is fed to home gateway
2. By plugging gateway into any electrical outlet, content is bridged to any HomePlug-enabled device
3. OFDM takes multiple signals of different frequencies and combines them to form one signal to avoid line “noise”
4. HomePlug network monitors power lines for “noise”.
For more on HomePlug visit their website: http://www.homeplug.org/home
If noise occurs on a particular frequency, OFDM engine shifts transmission to another frequency. OFDM also is used in the IEEE 802.16 WLL specification, also known as WiMax.
Wednesday, July 8, 2009
4G Mobile Network
4G Mobile Network: 4G is what the next, next generation cellular might be. The idea is simple – universal high-speed Internet access. The thinking is WiFi Internet access (at up to 10 megabits per second) with blanket coverage and fewer base stations than are needed in today’s cell phone networks. Firms including IPWireless, Flarion, Navini, ArrayComm and Broadstorm offer just such a blend. But these are proprietary solutions, so far. Such proposed 4G wireless-broadband systems can be seen in two ways: as a rival to coffee shop WiFi or as a wireless alternative to the cable modem and digital subscriber line (DSL) technologies that now provide broadband access to homes and offices. IPWireless sees their system as a fast internet connection that follows you around. Navini calls it “nomadic broadband”; ArrayComm’s term is “personal broadband”.
Mike Gallagher of Flarion, a firm backed by Cisco, likens WiFi to cordless phones that work within a limited range of a base-station whereas 4G is akin to mobile phones that work anywhere. Advocates of 4G technology argue that, unlike with 3G and WiFi, the business case for 4G is sound. Nobody is sure how commercial WiFi hotspots will make money. The number of connections per day at most hotspots is still tiny. But 4G is being priced like fixed-line broadband, a service for which millions of users worldwide are already willing to pay about $50 a month. 4G networks may be built initially in regions where cable and DSL are unavailable, in order to capitalize on pent-up demand for broadband. Some cell phone companies are said to be considering skipping 3G altogether in favor of 4G.
Source: Newton’s Telecom Dictionary, 2nd Edition; 2006
*4G Developments*
NTT DoCoMo has been testing a 4G system prototype with 4x4 MIMO called “VSF-OFCDM” at 100 MB/sec while moving and 1GB/sec while stationary and is planning on releasing the first commercial network in 2010.
Digiweb, an Irish fixed and wireless broadband company, announced that they have received license from ComReg (Irish Telecom regulator) for the provisioning of 4G mobile communications.
Verizon Wireless announced in September 2007 that it’s planning a joint effort with Vodafone to transition its networks to the 4G standard LTE. In December 2008, Verizon Wireless announced that they intend to build, design, and begin to roll out a LTE network by the end of 2009.
Sprint announced the offering of a 3G/4G connection plan (which is currently only available in Baltimore).
Source: http://en.wikipedia.org/wiki/4G
More on 4G, pervasive networks, and mesh routing to come…stay tuned!
Mike Gallagher of Flarion, a firm backed by Cisco, likens WiFi to cordless phones that work within a limited range of a base-station whereas 4G is akin to mobile phones that work anywhere. Advocates of 4G technology argue that, unlike with 3G and WiFi, the business case for 4G is sound. Nobody is sure how commercial WiFi hotspots will make money. The number of connections per day at most hotspots is still tiny. But 4G is being priced like fixed-line broadband, a service for which millions of users worldwide are already willing to pay about $50 a month. 4G networks may be built initially in regions where cable and DSL are unavailable, in order to capitalize on pent-up demand for broadband. Some cell phone companies are said to be considering skipping 3G altogether in favor of 4G.
Source: Newton’s Telecom Dictionary, 2nd Edition; 2006
*4G Developments*
NTT DoCoMo has been testing a 4G system prototype with 4x4 MIMO called “VSF-OFCDM” at 100 MB/sec while moving and 1GB/sec while stationary and is planning on releasing the first commercial network in 2010.
Digiweb, an Irish fixed and wireless broadband company, announced that they have received license from ComReg (Irish Telecom regulator) for the provisioning of 4G mobile communications.
Verizon Wireless announced in September 2007 that it’s planning a joint effort with Vodafone to transition its networks to the 4G standard LTE. In December 2008, Verizon Wireless announced that they intend to build, design, and begin to roll out a LTE network by the end of 2009.
Sprint announced the offering of a 3G/4G connection plan (which is currently only available in Baltimore).
Source: http://en.wikipedia.org/wiki/4G
More on 4G, pervasive networks, and mesh routing to come…stay tuned!
Tuesday, July 7, 2009
HSDPA (in W-CDMA)
HSDPA (in W-CDMA): High Speed Downlink Packet Access (HSDPA) is a packet-based data service in W-CDMA downlink with data transmission up to 8-10 Mbps (and 20 Mbps for MMO systems) over a 5MHz bandwidth in WCDMA downlink. HSDPA implementations includes Adaptive Modulation and Coding (AMC), Multiple-Input Multiple-Output (MIMO), Hybrid Automatic Request (HARQ), fast cell search, and advanced receiver design. In 3rd generation partnership project (3GPP) standards, Release 4 specifications provide efficient IP support enabling provision of services through an all-IP core network and Release 5 specifications focus on HSDPA to provide data rates up to approximately 10 Mbps to support pack-based multimedia services. MIMO systems are the work item in Release 6 specifications, which will support even high data transmission rates up to 20 Mbps. HSDPA is evolved from and backward compatible with Release 99 WCDMA systems.
Monday, July 6, 2009
3.5G Mobile Network
3.5G Mobile Network: a faster version of 3G wireless networks, 3.5G uses a technology called HSDPA, which is a significant enhancement to W-CDMA and can achieve speeds of up to 14.4 Mbps. HSDPA stands for High Speed Downlink Packet Access. It is a packet based data service feature of the WCDMA standard which provides a downlink with data transmission up to 8-10 Mbps (and 20 Mbps for MIMO systems) over a 5MHz bandwidth in WCDMA downlink. The high speeds of HSDPA is achieved through techniques including; 16 Quadrature Amplitude Modulation, variable error coding, and incremental redundancy. HSDPA is a technology upgrade to current UMTS networks.
Friday, July 3, 2009
3G Mobile Network
Third Generation Mobile System. Most commonly 3G networks are discussed as graceful enhancements of the GSM cellular standards. Thereby, existing GSM networks can be upgraded on a non-disruptive basis. The enhancements include greater bandwidth, more sophisticated compression techniques, and the inclusion of in-building systems. 3G networks will transmit data at 144 kilobits per second, or up to 2 megabits per second from fixed locations. This planned evolution of GSM is an integral part of the ITU-T’s vision of IMT-2000 (International Mobile Telecommunications for the year 2000), which clearly missed the target date of 2000. The aim of IMT-2000 is to harmonize worldwide 3G systems to provide global roaming.
3G has standardized (or will) three mutually incompatible standards: FDD, TDD, and CDMA2000. FDD and TDD are extensions of GSM architecture using CDMA technology in the air interface. CDMA2000 is the extension of IS95 air interface for wideband data applications. The three standards will compete with each other in the marketplace. In addition to the technical differences between the standards, there is a strong political background in the competition. FDD and TDD were proposed by European firms, and will be promoted worldwide as the heirs to GSM systems. CDMA2000 was the standard championed by Qualcomm, the USA based company with many patents in CDMA technology.
We will go into more detail on 3G in the upcoming WotD posts. Enjoy the holiday!
3G has standardized (or will) three mutually incompatible standards: FDD, TDD, and CDMA2000. FDD and TDD are extensions of GSM architecture using CDMA technology in the air interface. CDMA2000 is the extension of IS95 air interface for wideband data applications. The three standards will compete with each other in the marketplace. In addition to the technical differences between the standards, there is a strong political background in the competition. FDD and TDD were proposed by European firms, and will be promoted worldwide as the heirs to GSM systems. CDMA2000 was the standard championed by Qualcomm, the USA based company with many patents in CDMA technology.
We will go into more detail on 3G in the upcoming WotD posts. Enjoy the holiday!
Wednesday, July 1, 2009
2.5G and GPRS
2.5G Mobile Network: Second-and-a-half generation wireless. Refers to the additional features and functionality added to digital cellular phones, such as Internet access and messaging. The main feature added to 2.5G is GPRS, a mobile data communications service running at the speed of a dial-up landline.
GPRS: Want to connect your laptop to your cell phone and surf the web or send emails? GPRS is for you. GPRS stands for General Packet Radio Service. And it’s the always-on packet data service for GSM, which is the cell phone standard which most countries of the world use, including Europe, Australia, America (not all carriers obviously) and some parts of Asia. The idea is that you’ll connect your GPRS-equipped (also called 2.5G) cell phone to your laptop with a cable or insert a small GPRS-equipped PCMCIA card into your laptop and transmit. GPRS will be most useful for “bursty” data applications such as mobile Internet browsing and e-mail. GPRS has been demonstrated as fast as 115 Kbps. And in theory it can go that fast. But the reality is that you’ll get between 20Kbps and 50Kbps throughput—about the speed you get from your dial-up home landline.
One big advantage of GPRS is that it’s “always on” just like your DSL line, your cable modem or your office network. To send a data message you won’t have to waste a minute dialing a number and listening to the modems go through their interminable screeching/connection “dance”. GPRS is the primary feature of what has become known as 2.5G – the upgrade to today’s 2G cell phone network. 1XRTT is the CDMA equivalent of GPRS.
Source: Newton’s Telecom Dictionary 22nd edition; 2006
GPRS: Want to connect your laptop to your cell phone and surf the web or send emails? GPRS is for you. GPRS stands for General Packet Radio Service. And it’s the always-on packet data service for GSM, which is the cell phone standard which most countries of the world use, including Europe, Australia, America (not all carriers obviously) and some parts of Asia. The idea is that you’ll connect your GPRS-equipped (also called 2.5G) cell phone to your laptop with a cable or insert a small GPRS-equipped PCMCIA card into your laptop and transmit. GPRS will be most useful for “bursty” data applications such as mobile Internet browsing and e-mail. GPRS has been demonstrated as fast as 115 Kbps. And in theory it can go that fast. But the reality is that you’ll get between 20Kbps and 50Kbps throughput—about the speed you get from your dial-up home landline.
One big advantage of GPRS is that it’s “always on” just like your DSL line, your cable modem or your office network. To send a data message you won’t have to waste a minute dialing a number and listening to the modems go through their interminable screeching/connection “dance”. GPRS is the primary feature of what has become known as 2.5G – the upgrade to today’s 2G cell phone network. 1XRTT is the CDMA equivalent of GPRS.
Source: Newton’s Telecom Dictionary 22nd edition; 2006
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