Archive for December, 2007

Worldwide Interoperability for Microwave Access"Wimax"

WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. It is based on the IEEE 802.16 standard, which is also called WirelessMAN. The name WiMAX was created by the WiMAX Forum, which was formed in June 2001 to promote conformance and interoperability of the standard. The forum describes WiMAX as “a standards-based technology enabling the delivery of
last mile wireless broadband access as an alternative to cable and DSL.”
The terms “fixed WiMAX“, “mobile WiMAX“, “802.16d” and “802.16e” are frequently used incorrectly. Correct definitions are:
802.16d

Strictly speaking, 802.16d has never existed as a standard. The standard is correctly called 802.16-2004 and was developed by the IEEE 802.16 Task Group d. Therefore the project was called 802.16d, but the standard never was. However, since this standard is frequently called 802.16d, that term is also used in this article to assist readability.

802.16e

Just as 802.16d has never existed as a standard, neither has 802.16e. 802.16e is an amendment to 802.16-2004, and the amendment is properly referred to as 802.16e-2005. 802.16e-2005 is not a standard in its own right – since it is only an amendment, the original document (802.16-2004) has to be read and then the amendments added to it.

Fixed WiMAX

This is a phrase frequently used to refer to systems built using 802.16-2004 (‘802.16d‘) and the OFDM PHY as the air interface technology. Fixed WiMAX deployments do not cater for handoff between Base Stations, therefore the service provider cannot offer mobility.

Mobile WiMAX

A phrase frequently used to refer to systems built using 802.16e-2005 and the OFDMA PHY as the air interface technology. “Mobile WiMAX” implementations can be used to deliver both fixed and mobile services.

Uses

The bandwidth and reach of WiMAX make it suitable for the following potential applications:

  • Connecting Wi-Fi hotspots with each other and to other parts of the Internet.
  • Providing a wireless alternative to cable and DSL for last mile broadband access.
  • Providing high-speed data and telecommunications services.
  • Providing a diverse source of Internet connectivity as part of a business continuity plan. That is, if a business has a fixed and a wireless Internet connection, especially from unrelated providers, they are unlikely to be affected by the same service outage.
  • Providing nomadic connectivity.

Broadband access

Many companies are closely examining WiMAX for “last mile” connectivity at high data rates. The resulting competition may bring lower pricing for both home and business customers or bring broadband access to places where it has been economically unavailable. Prior to WiMAX, many operators have been using proprietary fixed wireless technologies for broadband services.

WiMAX access was used to assist with communications in Aceh, Indonesia, after the tsunami in December 2004. All communication infrastructure in the area, other than Ham Radio, was destroyed, making the survivors unable to communicate with people outside the disaster area and vice versa. WiMAX provided broadband access that helped regenerate communication to and from Aceh.

WiMAX was used by Intel to assist the FCC and FEMA in their communications efforts in the areas affected by Hurricane Katrina.

Subscriber units

WiMAX subscriber units are available in both indoor and outdoor versions from several manufacturers. Self-install indoor units are convenient, but radio losses mean that the subscriber must be significantly closer to the WiMAX base station than with professionally-installed external units.

As such, indoor-installed units require a much higher infrastructure investment as well as operational cost (site lease, backhaul, maintenance) due to the high number of base stations required to cover a given area. Indoor units are comparable in size to a cable modem or DSL modem. Outdoor units are roughly the size of a laptop PC, and their installation is comparable to a residential satellite dish.

With the advent of mobile WiMAX, there is an increasing focus on portable units. This includes handsets (similar to cellular smartphones) and PC peripherals (PC Cards or USB dongles). In addition, there is much emphasis from operators on consumer electronics devices (games terminals, MP3 players and the like); it is notable this is more similar to WiFi than 3G cellular technologies.

Mobile applications

Some cellular companies are evaluating WiMAX as a means of increasing bandwidth for a variety of data-intensive applications; Sprint Nextel announced in mid-2006 that it would invest about US$ 5 billion in a WiMAX technology buildout over the next few years. As of Friday, November 9, 2007, this project in partnership with Clearwire has been shelved, but the project could be revived with or without Clearwire once Sprint hires a new CEO.

On December 5, 2007, Bin Shen, Sprint’s VP of Product Management and Partnership Development, announced that Sprint’s WiMAX network will go live in a soft launch in Chicago, Baltimore, and Washington DC. Full commercial launch is still expected to be approximately spring of 2008. In December 2007 Wateen Telecom Pakistan Deployed the largest and the first in the world to roll-out WiMAX 802.16e network nationwide in 22 cities. In line with these possible applications is the technology’s ability to serve as a high bandwidth “backhaul” for Internet or cellular phone traffic from remote areas back to an Internet backbone.

Although the cost per user/point of WiMAX in a remote application will be higher, it is not limited to such applications, and may be an answer to reducing the cost of T1/E1 backhaul as well. Given the limited wired infrastructure in some developing countries, the costs to install a WiMAX station in conjunction with an existing cellular tower or even as a solitary hub are likely to be small in comparison to developing a wired solution. Areas of low population density and flat terrain are particularly suited to WiMAX and its range. For countries that have skipped wired infrastructure as a result of prohibitive costs and unsympathetic geography, WiMAX can enhance wireless infrastructure in an inexpensive, decentralized, deployment-friendly and effective manner.

Technical information

WiMAX is a term coined to describe standard, interoperable implementations of IEEE 802.16 wireless networks, similar to the way the term Wi-Fi is used for interoperable implementations of the IEEE 802.11 Wireless LAN standard. However, WiMAX is very different from Wi-Fi in the way it works.
Standards

The current WiMAX incarnation, Mobile WiMAX, is based upon IEEE Std 802.16e-2005, approved in December 2005. It is an amendment of IEEE Std 802.16-2004 and so the actual standard is 802.16-2004 as amended by 802.16e-2005 – the specifications need to be read together to understand them.

IEEE Std 802.16-2004 addresses only fixed systems. It replaced IEEE Standards 802.16-2001, 802.16c-2002, and 802.16a-2003.

IEEE 802.16e-2005

IEEE 802.16e-2005 improves upon IEEE 802.16-2004 by:

  • Adding support for mobility (soft and hard handover between base stations). This is seen as one of the most important aspects of 802.16e-2005, and is the very basis of ‘Mobile WiMAX‘.
  • Scaling of the Fast Fourier Transform (FFT) to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths (1.25-20 MHz). Constant carrier spacing results in a higher spectrum efficiency in wide channels, and a cost reduction in narrow channels. Also known as Scalable OFDMA (SOFDMA).
  • Improving NLOS coverage by utilizing advanced antenna diversity schemes, and hybrid-Automatic Retransmission Request (HARQ)
  • Improving capacity and coverage by introducing Adaptive Antenna Systems (AAS) and Multiple Input Multiple Output (MIMO) technology
  • Increasing system gain by use of denser sub-channelization, thereby improving indoor penetration
  • Introducing high-performance coding techniques such as Turbo Coding and Low-Density Parity Check (LDPC), enhancing security and NLOS performance
  • Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa
  • Enhanced Fast Fourier Transform algorithm can tolerate larger delay spreads, increasing resistance to multipath interference
  • Adding an extra QoS class (enhanced real-time Polling Service) more appropriate for VoIP applications.

802.16d vendors point out that fixed WiMAX offers the benefit of available commercial products and implementations optimized for fixed access. It is a popular standard among alternative service providers and operators in developing areas due to its low cost of deployment and advanced performance in a fixed environment. Fixed WiMAX is also seen as a potential standard for backhaul of wireless base stations such as cellular, WiFi or even Mobile WiMAX.

SOFDMA (used in 802.16e-2005) and OFDM256 (802.16d) are not compatible so most equipment will have to be replaced if an operator wants or needs to move to the later standard. However, some manufacturers are planning to provide a migration path for older equipment to SOFDMA compatibility which would ease the transition for those networks which have already made the OFDM256 investment. Intel provides a dual-mode 802.16-2004 802.16-2005 chipset for subscriber units. This affects a relatively small number users and operators.

http://en.wikipedia.org/wiki/WiMAX


Posted 31 Dec 2007 by narmadi
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Code division multiple access (CDMA)

Code division multiple access (CDMA) describes a communication channel access principle that employs spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code). In communications technology, there are only three domains that can allow multiplexing to be implemented for more efficient use of the available
channel bandwidth and these domains are known as time, frequency and space.

CDMA divides the access in signal space. By contrast, time division multiple access (TDMA) divides access by time, while frequency-division multiple access (FDMA) divides it by frequency. CDMA is a form of “spread-spectrum” signaling, since the modulated coded signal has a much higher bandwidth than the data being communicated.

An analogy to the problem of multiple access is a room (channel) in which people wish to communicate with each other. To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different directions (spatial division). In CDMA, they would speak different languages. People speaking the same language can understand each other, but not other people. Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only users associated with a particular code can understand each other.

Interestingly, CDMA is based on a patent granted in 1942 to two people, one of which was world famous actress Hedy Lamarr. Lamarr, probably best known for doing one of the first nude scenes in a major motion picture, worked with a partner-composer George Antheil-on a system that would make radio controlled torpedoes more difficult to detect through an early version of frequency hopping. Their system was inspired by the mechanical rolls that make self playing pianos work.

CDMA is also the current name for the cellular technology originally known as IS-95. Developed by Qualcomm and enhanced by Ericsson, CDMA is characterized by high capacity and small cell radius. CDMA also refers to digital cellular telephony systems that use this multiple access scheme, as pioneered by QUALCOMM, and W-CDMA by the International Telecommunication Union (ITU), which is used in GSM’s UMTS.

CDMA has been used in many communications and navigation systems, including the Global Positioning System and the OmniTRACS satellite system for transportation logistics.
The terms are used to refer to CDMA implementations. The original US standard defined by QUALCOMM was known as IS-95, where IS refers to an Interim Standard of the US Telecommunications Industry Association. IS-95 is often referred to as the second generation (2G) cellular, or as cdmaOne (the QUALCOMM brand name). CDMA has been submitted for approval as a mobile air interface standard to the International Telecommunication Union (ITU).

Whereas Global System for Mobile Communications (GSM) is a specification of an entire network infrastructure, CDMA relates only to the air interface — the radio portion of the technology. For example, GSM specifies an infrastructure based on internationally approved standard, while CDMA allows each operator to provide network features it finds suitable. On the air interface, the signalling suite (GSM: ISDN SS7) work has been progressing to harmonise these features.

After some revisions, IS-95 was superseded by the IS-2000 standard (CDMA2000). This standard was introduced to meet some of the criteria laid out in the IMT-2000 specification for third generation (3G) cellular. It is also called 1xRTT which means “1 times Radio Transmission Technology” because IS-2000 uses the same 1.25 MHz carrier shared channel as the original IS-95 standard. A related scheme, called 3xRTT, uses three 1.25 MHz carriers for a 3.75 MHz bandwidth that would allow higher data burst rates for an individual user, but the 3xRTT scheme has not been commercially deployed.

More recently, QUALCOMM has led the creation of a new CDMA-based technology called Evolution-Data Optimized (1xEV-DO, or IS-856), which provides the higher packet data transmission rates required by IMT-2000 and desired by wireless network operators.
This CDMA system is frequently confused with a similar but incompatible technology called Wideband Code Division Multiple Access (W-CDMA) which is the basis of the W-CDMA air interface. The W-CDMA air interface is used in the global 3G standard UMTS and the Japanese 3G standard FOMA, by NTT DoCoMo and Vodafone; however, the CDMA family of US national standards (including cdmaOne and CDMA2000) are not compatible with the W-CDMA family of ITU standards.

Another important application of code division multiplexing — predating and distinct from CDMA — is the Global Positioning System (GPS). The QUALCOMM CDMA system includes very accurate time signals (usually referenced to a GPS receiver in the cell base station), so cell phone CDMA-based clocks are an increasingly popular type of radio clock for use in computer networks. The main advantage of using CDMA cell phone signals for reference clock purposes is that they work better inside buildings, thus often eliminating the need to mount a GPS antenna outside a building.

http://en.wikipedia.org/wiki/Code_division_multiple_access


Posted 31 Dec 2007 by narmadi
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Global System for Mobile communications "GSM"

Global System for Mobile communications (GSM: originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world. Its promoter, the GSM Association, estimates that 82% of the global mobile market uses the standard. GSM is used by over 2 billion people across more than 212 countries and territories.

Its ubiquity makes international roaming very common between mobile phone operators, enabling subscribers to use their phones in many parts of the world. GSM differs from its predecessors in that both signaling and speech channels are digital call quality, and so is considered a second generation (2G) mobile phone system. This has also meant that data communication were built into the system using the 3rd Generation Partnership Project (3GPP).

The key advantage of GSM systems to consumers has been better voice quality and low-cost alternatives to making calls, such as the Short message service (SMS, also called “text messaging“). The advantage for network operators has been the ease of deploying equipment from any vendors that implement the standard. Like other cellular standards, GSM allows network operators to offer roaming services so that subscribers can use their phones on GSM networks all over the world.

Newer versions of the standard were backward-compatible with the original GSM phones. For example, Release ‘97 of the standard added packet data capabilities, by means of General Packet Radio Service (GPRS). Release ‘99 introduced higher speed data transmission using Enhanced Data Rates for GSM Evolution (EDGE).

History

In 1982, the European Conference of Postal and Telecommunications Administrations (CEPT) created the Groupe Spécial Mobile (GSM) to develop a standard for a mobile telephone system that could be used across Europe. In 1987, a memorandum of understanding was signed by 13 countries to develop a common cellular telephone system across Europe.

In 1989, GSM responsibility was transferred to the European Telecommunications Standards Institute (ETSI) and phase I of the GSM specifications were published in 1990. The first GSM network was launched in 1991 by Radiolinja in Finland with joint technical infrastructure maintenance from Ericsson. By the end of 1993, over a million subscribers were using GSM phone networks being operated by 70 carriers across 48 countries.

Technical details

GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity. GSM networks operate in four different frequency ranges. Most GSM networks operate in the 900 MHz or 1800 MHz bands. Some countries in the Americas (including Canada and the United States) use the 850 MHz and 1900 MHz bands because the 900 and 1800 MHz frequency bands were already allocated. The rarer 400 and 450 MHz frequency bands are assigned in some countries, notably Scandinavia, where these frequencies were previously used for first-generation systems.

In the 900 MHz band the uplink frequency band is 890–915 MHz, and the downlink frequency band is 935–960 MHz. This 25 MHz bandwidth is subdivided into 124 carrier frequency channels, each spaced 200 kHz apart. Time division multiplexing is used to allow eight full-rate or sixteen half-rate speech channels per radio frequency channel. There are eight radio timeslots (giving eight burst periods) grouped into what is called a TDMA frame. Half rate channels use alternate frames in the same timeslot. The channel data rate is 270.833 kbit/s, and the frame duration is 4.615 ms. The transmission power in the handset is limited to a maximum of 2 watts in GSM850/900 and 1 watt in GSM1800/1900.

GSM has used a variety of voice codecs to squeeze 3.1 kHz audio into between 5.6 and 13 kbit/s. Originally, two codecs, named after the types of data channel they were allocated, were used, called Half Rate (5.6 kbit/s) and Full Rate (13 kbit/s). These used a system based upon linear predictive coding (LPC). In addition to being efficient with bitrates, these codecs also made it easier to identify more important parts of the audio, allowing the air interface layer to prioritize and better protect these parts of the signal.

GSM was further enhanced in 1997 with the Enhanced Full Rate (EFR) codec, a 12.2 kbit/s codec that uses a full rate channel. Finally, with the development of UMTS, EFR was refactored into a variable-rate codec called AMR-Narrowband, which is high quality and robust against interference when used on full rate channels, and less robust but still relatively high quality when used in good radio conditions on half-rate channels.

There are four different cell sizes in a GSM network—macro, micro, pico and umbrella cells. The coverage area of each cell varies according to the implementation environment. Macro cells can be regarded as cells where the base station antenna is installed on a mast or a building above average roof top level. Micro cells are cells whose antenna height is under average roof top level; they are typically used in urban areas. Picocells are small cells whose coverage diameter is a few dozen meters; they are mainly used indoors. Umbrella cells are used to cover shadowed regions of smaller cells and fill in gaps in coverage between those cells.

Cell horizontal radius varies depending on antenna height, antenna gain and propagation conditions from a couple of hundred meters to several tens of kilometers. The longest distance the GSM specification supports in practical use is 35 kilometres (22 mi). There are also several implementations of the concept of an extended cell, where the cell radius could be double or even more, depending on the antenna system, the type of terrain and the timing advance.

Indoor coverage is also supported by GSM and may be achieved by using an indoor picocell base station, or an indoor repeater with distributed indoor antennas fed through power splitters, to deliver the radio signals from an antenna outdoors to the separate indoor distributed antenna system. These are typically deployed when a lot of call capacity is needed indoors, for example in shopping centers or airports. However, this is not a prerequisite, since indoor coverage is also provided by in-building penetration of the radio signals from nearby cells.

The modulation used in GSM is Gaussian minimum-shift keying (GMSK), a kind of continuous-phase frequency shift keying. In GMSK, the signal to be modulated onto the carrier is first smoothed with a Gaussian low-pass filter prior to being fed to a frequency modulator, which greatly reduces the interference to neighboring channels (adjacent channel interference).

Interference with audio devices

This is a form of RFI, and could be mitigated or eliminated by use of additional shielding and/or bypass capacitors in these audio devices. However, the increased cost of doing so is difficult for a designer to justify.

It is a common occurrence for a nearby GSM handset to induce a “dit, dit di-dit, dit di-dit, dit di-dit” output on PA’s, wireless microphones, home stereo systems, televisions, computers, cordless phones, and personal music devices. When these audio devices are in the near field of the GSM handset, the radio signal is strong enough that the solid state amplifiers in the audio chain act as a detector. The clicking noise itself represents the power bursts that carry the TDMA signal. These signals have been known to interfere with other electronic devices, such as car stereos and portable audio players.

Via: wikipedia


Posted 31 Dec 2007 by narmadi
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Posted 27 Dec 2007 by narmadi
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Download Regulations

Here are some Telecommunication regulation in Indonesia. feel free for free download just click the under line (yellow) words below.

LAW OF THE REPUBLIC OF INDONESIA
NO. 36 OF 1999 ON TELECOMMUNICATIONS ?

GOVERNMENT REGULATION OF THE REPUBLIC OF INDONESIA
NUMBER 52 YEAR 2000 CONCERNING TELECOMMUNICATIONS OPERATION ?

REGULATION OF THE MINISTER OF COMMUNICATIONS AND INFORMATION NUMBER: 13/P/M.KOMINFO/8/2005
REGARDING PROVISION OF TELECOMMUNICATIONS VIA SATELLITE
BY THE MERCY OF GOD ALMIGHTY
THE MINISTER OF COMMUNICATIONS AND INFORMATION ?

REGULATION OF THE MINISTER OF COMMUNICATION AND INFORMATION TECHNOLOGY
NUMBER: 07/PER/M.KOMINFO/2/2006
ON THE TERMS OF THE USE OF 2.1 GHz RADIO FREQUENCY BAND FOR THE PROVISION OF MOBILE CELLULAR NETWORK
WITH THE GRACE OF GOD ALMIGHTY
THE MINISTER OF COMMUNICATION AND INFORMATION TECHNOLOGY ?

GENERAL TERMs OF TELECOMMUNICATION EQUIPMENT TESTING (SK NO. 1A/KABALAI/2005) ?


Posted 12 Dec 2007 by narmadi
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