An Introduction to 4G Technology
The fourth generation of wireless standards for cellular systems is 4G, the planned successor to the 3G standard. The ITU (International Telecommunications Union) has specified that the peak speed requirements for the 4G standard are to be 100Mbps for a mobile connection (such as in a car) and 1Gbps for stationary connections (such as sitting at a computer). 4G services that meet these requirements are not publically available yet (as of June 2011) but telecommunications providers are looking to upgrade their infrastructure to cater for 4G services in the not too distant future. The 4G service is set to offer a fast and secure all-IP, roaming mobile broadband solution to devices such as laptops with wireless 4G modems, 4G smartphone mobile phones and other 4G mobile devices that require internet access with speed intensive facilities being made available, including on-demand HD television, IP telephony, on-demand gaming and, of course, high speed internet access.
Currently marketed technologies such as LTE (Long Term Evolution) and WiMAX have been around for a few years and are being marketed as 4G whilst not meeting the requirements set by the ITU. It was recently announced that these services could continue to be marketed as 4G as they are precursors to the IMT-Advanced, 4G standard whilst also operating on the same basis of technology; however, these should really be considered as "Pre-4G" or "3.9G" as they technically do not offer the required data rates of (stationary) 1Gbps.
The ITU has recognised two standards that are planned to meet the 4G IMT-Advanced requirements put forward by the two groups, 3GPP and IEEE. These are the LTE Advanced and WirelessMAN-Advanced (WiMAX-Advanced) standards and will almost certainly abandon the old spread system technology found in 3G systems for OFDMA and other equalisation schemes, use MIMO technology, channel-dependant scheduling and dynamic channel allocation... all technologies that are being found on new, modern wireless networking equipment.
The use of the 4G service will be very similar to that of the 3G service whilst offering much higher data transfer rates and therefore allowing either more speed intensive applications or more users to experience good speeds whilst only connected through 1 carrier. Applications could include:
- 4G Ultra high speed internet access - E-mail or general web browsing is available.
- 4G Data intensive interactive user services - Services such as online satellite mapping will load instantly.
- 4G Multiple User Video conferencing - subscribers can see as well as talk to more than one person.
- 4G Location-based services - a provider sends wide spread, real time weather or traffic conditions to the computer or phone, or allows the subscriber to find and view nearby businesses or friends whilst communicating with them.
- 4G Tele-medicine - a medical provider monitors or provides advice to the potentially isolated subscriber whilst also streaming to them related videos and guides.
- 4G HDTV - a provider redirects a high definition TV channel directly to the subscriber where it can be watched.
- 4G High Definition Video on demand - a provider sends a movie to the subscriber.
- 4G Video games on demand - a provider sends game data directly to the subscriber where they can play in real time.
The other main application that 4G could make available that 3G in general did not, or could not, is the capability to be used as a main internet access point within homes or businesses whilst catering for multiple connections at high speeds. If the 1Gbps rate is available within these areas, the speeds would be many times more than those that are currently publicly available and this application could be very useful for creating 4G wireless networks that can be located in rural areas with no access to the high speed, cabled, broadband grid.
The IMT-Advanced Standard (4G) requires the following specifications to be met:
- It must be based upon an all-IP packet switched network
- Peak data rates must be up to 100Mbps in high mobility situations and up to 1Gbps for low mobility/stationary applications
- Network resources should be utilised and dynamically shared to support more users on same connection
- Channel bandwidth should be scalable between 5, 20 and up to 40MHz
- Spectral efficiency should be no less than 15bit/s/Hz and 6.75bit/s/Hz for outdoor downlink and uplink usage respectively
- Spectral efficiency should be no less than 3bit/s/Hz and 2.25bit/s/Hz for indoor downlink and uplink usage respectively
- Connection transitions across heterogeneous networks should be smooth
- A high quality of service must be available to allow the next generation of multimedia support on mobile devices
LTE (Long Term Evolution) has experienced peak download rates of 326.4 Mbps and 172.8 Mbps for 4x4 and 2x2 MIMO antennas respectively when using 20 MHz of spectrum and peak upload rates of 86.4 Mbps for every 20 MHz of spectrum using a single antenna. This means that it does not quite meet the 4G requirements but it is still often branded as 4G by telecommunications providers as it offers a considerable increase in performance over 3G. Its radio interface is often referred to as E-UTRA (Evolved UMTS Terrestrial Radio Access).
3GPP LTE Advanced
4G LTE Advanced is not a new technology but rather an enhancement to the existing LTE standard by using multiplexing and additional spectrum range to achieve the speeds required for 4G; whilst help for system capacity usage is dealt with by co-ordinated multi point transmissions. 4G LTE-Advanced can use up to 8x8 MIMO antennas and 128 QAM (Quadrature Amplitude Modulation) giving performance of almost 3.3Gbps peak download rates per sector of the base station using 100MHz aggregated bandwidth under perfect conditions. With new developing technologies such as smart antennas and advanced network infrastructures, 4G LTE Advanced will take a good few years to become fully developed and integrated.
IEEE WiMAX and WiMAN-Advanced
The WiMAX (IEEE 802.16e) standard offers peak data rates of 128Mbps downlink and 56Mbps uplink over 20MHz wide channels whilst the new standard in development, 4G WiMAN-Advanced (802.16m) is targeting the requirements to be fully 4G using 64Q QAM, BPSK and MIMO technologies to reach the 1Gbps rate. It is predicted that in an actual deployment, using 4X2 MIMO in an urban microcell application using a 20 MHz TDD channel, the 4G WiMAN-Advanced system will be able to support 120Mbps downlink and 60Mbps uplink per site concurrently. WiMAX applications are already in use in many countries globally but research in 2010 gave results that showed only just over 350 set ups were actually in use. Many previous WiMAX operators were found to have moved to LTE along with Yota, who were the largest WiMAX operator in the world.
Below is a comparison table listing the current and proposed 4G systems along with other related systems:
||128 (20MHz b'width)
||56 (20MHz b'width)
||WiMAX update IEEE 802.16m expected to offer peak rates of at least 1 Gbps fixed speeds and 100Mbps to mobile users.
||UMTS / 4GSM
||OFDMA / MIMO / SC-FDMA
||100 (20MHz b'width)
||50 (20 MHz b'width)
||LTE-Advanced update expected to offer peak rates up to 1 Gbps fixed speeds and 100 Mb/s to mobile users.
||Mobile Internet mobility up to 200mph
||Mobile range 30km (18 miles) and Extended range 55 km (34 miles)
||OFDM / MIMO
||300 (using 4x4 configuration in 20MHz bandwidth) or 600 (using 4x4 configuration in 40MHz 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 (310km & 382km)
||HC-SDMA / TDD / MIMO
||Speed: 250km/h, Spectral Efficiency: 13 bits/s/Hz/cell, Spectrum Reuse Factor: "1", Cell Radius: 3-12 km
||TDMA / FDD
||3GPP Release 7
||CDMA / FDD
||HSDPA widely deployed. Typical downlink rates today 2 Mbps, ~200 kbps uplink; HSPA+ downlink up to 56 Mbps.
||CDMA / FDD / MIMO
||UMTS / 3GSM
||CDMA / TDD
||Reported speeds according to IPWireless using 16QAM modulation similar to HSDPA+HSUPA
||Succeeded by EV-DO for data use, but still is used for voice and as a failover for EV-DO
|EV-DO 1x Rev. 0
||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.
|EV-DO 1x Rev.A
BT is planning to launch a trial of 4G LTE technology in the rural areas near Newquay soon and is hopeful to roll out the 4G LTE service by 2014. O2 are planning to use Slough as a testing ground and has planned with Huawei to install 4G LTE technology in six masts across the area to allow users to communicate via HD video conferencing and play high end video games whilst being mobile.
Watch this space!