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Wireless WAN

Technical Proposals

 

There are a few initial fundamental issues that have to be resolved in order to accelerate the now imminent reconstruction of Afghanistan. The following illustrates these issues.

 

1. Communication

within Kabul and with the outside world, both in voice and data traffic, especially for the government in order to demonstrate the effectiveness of government to the donor community and establish order in the processes of governmental procedures. To provide for databases and programs in order to  establish the following criteria:

 
  • Database of persons working for the government their role and location, salary etc in order to establish a budget.
  • Database of works being carried out by the government, again to measure effectiveness, establish international tenders etc. and therefore prepare for effective budgeting and transparency.
  • Individual programs to facilitate governmental tasks such as for the health, education, civil service , civil aviation etc.
  • Database of Custom and excise controls etc.
  • Database of all foreign office staff and their role incorporating a private secure email communication facility for government.
  • Database of all foreign entities and their role in order to outline and coordinate their activity.
  • Other databases as and when called for.
To initialize the above proposal the following would have to be undertaken. To budget for the following equipment to be bought and sent immediately to Kabul.  
costs:
  • Servers    ~  4 x $2500 ( Servers to house and distribute the data)
  • PC's        ~  250 x $550 (Pentiums for operators)
  • Node Pair Microwave   ~  15 x $7000 (10 Mb/s up to 5 KM communication device)
  • generators   ~  5 x $350 (In case there is an extended Power Failure)
  • Power Fail   ~  10 x $150 (Batteries in case there is a Power failure)
  • Hubs & switches    ~  30 x $150 (Communication and distribution devices)
  • Desks      ~  250 x $75 ( Desks for operators)
  • Chairs      ~  250 x $50 (Chairs for operators)
  • Cable cat 5   ~  3Km   ~  $1500 (cabling required for buildings)
  • Software   ~   $30,000 (Operating Systems, Security, Databases, Intranet etc)
Sub total $323,000

The above list is preliminary and is not exhaustive, but will establish for a private WAN (Wide Area Network) for the governmental buildings only. The 250 operators can be anywhere with the buildings in Kabul. No wiring is required between building and data interception will be practically impossible. Once established the ability for the government to access data immediately will be available. In order to connect to the outside world, the Intelsat facility would have to be re-installed at Telecom House Kabul. This will require for a 5 Meter Antennae and other equipment so as to establish :

 

Additionally, an official Afghanistan Website should be established, to give accountability and information, feedback and establish direct data communication with Afghans abroad, with the ability for those Afghans to write proposals, get direct information etc etc. ( The Website and public domain data will have to be housed outside Afghanistan initially and be updated from Kabul)

Equipment and Technology

Spread Spectrum

Spread spectrum radio is a lower cost, convenient way to connect LANs between buildings . Spread spectrum links come with a wide range of performance availability, from 1 Mbp to 100 Mbps, and operate in the license-free ISM (Industrial, Scientific and Medical) bands. Spread spectrum radio is quick to implement and can be a very effective alternative to fiber or telephone company connectivity.

To obtain the most out of the system you choose, the quality of the installation is paramount. A clear signal will allow the system to perform better because packets do not have to be retransmitted. Retransmissions that eat up bandwidth need to be avoided at all costs.

Most spread spectrum products may be considered customer-installable when there is a clear line of sight (LOS) between buildings. Typical, easy installations are across the parking lot or down the street. At the same time, customer installed systems are sometimes a frustrating experience or more difficult than they need to be due to a lack of knowledge about the techniques professionals use. The longer the path of transmission, the harder it gets. To start out on the right foot, a path analysis is a necessity.

The path analysis includes: the determination of line of sight, identification of potential obstacles, calculation of path loss, power required to make a good link and definition of the appropriate antennae.

Defining Line of Sight

LOS, or line of sight, means just what it says ... antennas can see each other. It does not mean that you can see a sparse outline of the target building through a forest of trees or that you know where the building is even though you cannot actually see it. For longer distances, clearance above objects at the centre of the transmission path becomes important. The centre path of the signal would be found if you were to imagine taking a string and connecting the antennas end to end. Clear line of sight includes clearance below the string and above all objects so that the radio signal can propagate without reflection over the path. A rule of thumb is to have 12 feet per mile of clearance at the centre of the path between the two points you are connecting. How can you obtain line of sight? The best way is to get on top of the building and look before you buy. Most often, if you can see the building or part of it, there is a way to obtain line of sight. Poles or towers can be installed or you can hop to a structure that is a high point that can see both buildings to repeat the signal. In many cases permission to mount an antenna is only a phone call away. For example, five schools in Illinois use two local commercial grain elevators to repeat a signal to connect to the Internet.

How Much Power Do I Need?

In the U.S. power is limited for unlicensed ISM bands to 36 dB or 4 watts effective rated power (ERP). The ERP is measured by adding the dB's from the radio plus the gain from the antenna minus the losses from cable, connectors, lightening arrestor and filter, if any. Decibels or dB's are simple in concept but confusing for most to determine. Antenna gain is a measure of the directionality of the antenna or how narrow the transmission beam is when it focuses the energy from the radio. The more directional an antenna, the more likely it may be used to overcome poor line of sight clearance or radio interference and the greater the achievable distance. A radio's receiver sensitivity or receive threshold is key in the professional path analysis to determine power requirements. Receive threshold is the lowest signal strength at which a radio can differentiate its partner's signal and interpret the results of the transmission. Receive thresholds for spread spectrum radio are generally about -80 dB or .00000001 milliwatts. It is difficult to imagine how a device can pull from the air, identify and understand such a small amount of energy travelling at the speed of light, but that is the miracle of radio. Given the small receive power levels available to make the connection, it is important to align antennas for maximum signal strength. Better wireless systems can identify relative signal strength at the base station using built-in diagnostics.

In summary, implementation of a spread spectrum wireless link can have many benefits but, unless you are shooting across the street or down the block, professional installation may pay for itself in a faster link, less hassle and greater satisfaction.

The usable portion of the radio spectrum is huge ranging from approximately 6 kHz to 300 GHz. Because radio is so well suited to information transmission, however, almost all of the spectrum is already reserved for specific uses. Alas, because bandwidth is so scarce and valuable, the frequencies allocated for unlicensed networking are what one might call junk frequencies ones commercial users are unlikely to want. The 2.4- GHz band, for example, is subject to interference from microwave ovens, and the signals have difficulty penetrating trees, heavy snow, or anything at all that contains water. (the water absorbs a portion of the signal and is heated, just as in a microwave oven.) The 900-mHz band is often plagued by interference from medical and scientific equipment, cordless phones, wireless stereo speakers, and similar devices.  Unlicensed users of the band are considered to be secondary users. They take a back seat to licensed, or primary, users, who can transmit stronger signals and are subject to fewer restrictions. A high-power primary user such as a TV station or a vehicle location system can render an unlicensed frequency band useless to anyone else in the vicinity, including wireless LANs. Unlicensed users have no recourse - even if they've already spent tens of thousands of dollars on wireless networking equipment.  The requirements imposed by the regulations on unlicensed wireless networking equipment are relatively simple. First, the strength of the signal is limited-usually to less than I watt. Second, the signal must be transmitted using one of two spread-spectrum methods. The signal must either be spread out over a certain range of frequencies or hop among a certain minimum number of narrow slots each second.

SPREAD SPECTRUM HISTORY & PROBLEMS  The idea of spread-spectrum radio transmission was proposed by the US military who was seeking ways to prevent radio signals from being monitored or blocked by hostile parties. The two inventors came up with the notion of changing the frequency of a transmission at regular intervals faster than the enemy could retune.  A special receiver that knew the frequency-hopping pattern could follow it and pick up the entire transmission. The hopping patterns were controlled by the punched holes in piano rolls became known as frequency-hopping spread spectrum (FHSS).

Later, as digital logic became popular, an- other kind of spread spectrum was developed direct-sequence spread spectrum (DSSS). In this method of transmission, the signal does not hop from one frequency to another but is passed through a spreading function and distributed over the entire band at once. DSSS usually provides slightly higher data rates and shorter delays than FHSS, because the transmitter and receiver don't have to spend time retuning.

  Both FHSS and DSSS are resistant to interference from conventional radio transmitters. Because the signal doesn't stay in one place on the band, FHSS can elude a jammer – (a transmitter designed to block radio transmissions on a given frequency). DSSS avoids interference by configuring the spreading function in the receiver to concentrate the desired signal but spread out and dilutes any interfering signal.

Spread-spectrum radio is good at dodging interference from conventional sources – (signals that stay in one narrow area of the frequency band and don't move. it doesn't  always do as well when there are other spread ,spectrum systems operating nearby, though. The more frequency-hopping transmitters operating on a band, the more likely it is that one or more of them will hop to the same frequency at the same time, garbling data that must be retransmitted. DSSS is better at resisting noise up to a certain point. However, if the combined interference throughout the band rises above a certain level, throughput dramatically drops-nearly to zero. Unfortunately, it only takes a few nearby FHSS systems to cripple a DSSS system. On the other hand, because a DSSS system is always transmitting on every frequency in the band, a nearby FHSS system may be unable to find any clear channel to hop to. In the presence of interference, FHSS usually degrades more gracefully than DSSS, but neither works well when competing at close range.

Directional antennas can sometimes help a node focus on the system with which it must communicate and ignore interference from others. However, as a general rule, when two transmitters compete for the same bandwidth, the one that expends more energy per bit of data wins the battle.

Unfortunately, because the total energy each device can emit is limited by the FCC, the transmitter trying to send data at the highest speed. say - 10 Mbps instead of 1 Mbps - loses. The newest equipment can be hobbled by gear that's older and cheaper.

Another problem that can plague wireless networks is called the hidden transmitter  problem. Suppose a wireless network is implemented as a sort of Ethernet-in-the-air-any node can speak as long as it doesn't hear anyone else transmitting. This works well if all the nodes can hear one another. However, in real life, physical obstacles sometimes prevent some nodes in a network from being able to tell when another is transmitting.  

TOWER OF BABEL If all the transmitters on a given band would follow the same protocol, the number of collisions would be small. Unfortunately, there are many wireless networking - each of these schemes uses a unique protocol that the others do not under- stand. So although devices of the same type will cooperate, devices of different types won't know how to keep out of one another's way. (Many older wireless devices, including proprietary wireless LANs and cordless phones, observe no etiquette at all and so will never avoid collisions.) Because the FCC regulations do not require users of a given band to observe a common etiquette, many devices do not cooperate even when it might be in their best interest to do so.

Compounding this problem is another loop-hole in the FCC regulations. The regulations limit the strength of the signal that each transmitter can emit but don't limit the total number of transmitters any one user can operate, nor how close together those transmitters can be. For example, the Metricom Ricochet network, which operates on the 900-MHz unlicensed band, uses hundreds of transmitters attached to utility poles to provide wireless Internet service to an entire neneighbourhoodr city. To penetrate building walls and overcome interference, each transmitter can increase its power, if necessary, to the FCC-allowed maximum. The result: If you try to operate wire- less networking equipment in the same unlicensed public band, you may find your equipment swarmed by dozens of transmitters, each cranking up the power to drown you out.

Many wireless LANs allow nodes to roam as much as 1,000 feet from the base station. Unfortunately, the further you stray from the hub, the more likely you are to find yourself closer to a source of interference other than your own base station. This phenomenon sometimes causes perplexing interference problems in city office buildings. Two tenants who each install wireless LANs on their floors can make life difficult for one another. Likewise, a 900-mHz or 2.4-GHz cordless phone in a nearby office can sometimes render a wireless LAN inoperable.

go to A wireless Tutorial section

Design Option ­ 11 Mbps system (802.11b)
One potential solution would offer the Capital a shared 11 Mbps network that would connect all of the Government buildings in the district. This scenario assumes line-of-sight.
Assuming the district could mount a tower on Telecom House the estimated costs for establishing a wireless network to all Departments would be approximately $8,000 per node for Point to Point connection using the 5800 Wavespan. This is a one-time cost. These electronics have an expected lifetime of four (6) years.
One-time installation and configuration may be estimated at $1,000 per site (not including tower installation, if needed).
Ongoing maintenance costs may be estimated at $400 per year per site
In addition, the cost of a tower on which to place an antennae varies from   ~  $6,300 for a self-supported light-duty 50 foot tower, to   ~  $100,000 for a heavy-duty 200 foot tower (including installation and cabling connections, but not including engineering analysis.) To estimate this cost more accurately, an engineering study would be required. Engineering fees for such a study may be estimated at $7,000.

Standards-based Wireless Links
This technology allows transmission of up to 11 Mbps (actual tested systems deliver approximately 7 Mbps) to transport data traffic between multiple buildings at a time. Many companies now offer these devices for sale and prices have come down quite significantly.
This solution was designed for data communications and cannot carry standard analog voice or video. However, if voice and video signals are didigitised they can then be transported (H323 standard VoIP). Most systems do not set a higher priority for this traffic, in order that data delivery (the priority) is not interrupted. We don't recommend attempting to send voice and video over this type of link, however facilities for this will be available in the eventuality of a failure in Kabul Telecom , government communications will be uuninterrupted
There are proprietary variations on these systems that add one or two T-1 emulated circuits at extra cost.

Higher bandwidth wireless
The Wavespan brand model Stratum 100 is representative of a high-bandwidth radio frequency design that uses newly available unlicensed frequencies. Although Afghanistan does not have such restrictions, the rest of the developed nations have airwave restrictions and designs have been appropriately incorporated to adhere to those standards
This system can carry 100 Mbps full duplex data together with two (2) T-1 type interfaces for voice or video applications and has a range of up to five (5) miles. The T-1 feature is a distinct advantage over other wireless options if the government chooses to use compressed video (for videoconferencing or training) among buildings.
Poor weather conditions would not affect this system's operation.
A typical two-building interconnection would cost $22,000 (latest price), including installation (but not tower.) , for a total of $110,000. If one or more towers are necessary,
Due to costs for the amount of bandwidth, if the government desires greater than 11 Mbps bandwidth, we recommend a fiber solution to be installed in the future, and have the initial wireless as a backup.

The Wavespan 5800

Price @$3700-$23000 .. Cables should be custom cut, tested and terminated with N-type connectors. suggestion for the use of LMR 400 or LMR 600 coaxial cable with proper lightning protection and a grounding system

This was Wavespan which was bought out by Proxim http://www.proxim.com/products/all/stratum/

img3fin

Data Rate (FDX) Range (18"x18" Antenna) Modulation
10 Mbps 5.0 Miles 256-QAM
8 Mbps 8.0 Miles 64-QAM
6 Mbps 12.0 Miles 16-QAM
3 Mbps 20.0 Miles
strat100.jpg (7424 bytes)
This solution costs between $5000 to 23000 depending on the distance required.

An alternative would be to use a cheaper system from Lucent Technologies.

LUCENT ORINOCO RADIO BACKBONE

is yet another RF device for point to point communications. KIT
$3,149.00


Point-to-Point Radio Backbone Kit

The Point-to-Point Radio Backbone Kit is an easy to install, highly reliable 11 Mbit/s building-to-building Wireless LAN connectivity solution. The kit includes all the necessary hardware, software and management components needed to establish a licence free 2.4 GHz wireless LAN bridge that spans up to 6 miles under clear line of sight conditions. A low cost solution relative to regulated frequency products.

Easy to install and manage the point-to-point kit offers full interoperability with existing and new LAN technology. The advanced technology, including full routing functionality, offers all the benefits of 802.11b, as well as superior radio technology that delivers unbeatable performance resulting in superior range and throughput.

FEATURES

  • High performance 2.4GHz integrated 11 Mbit/s radio
  • 128-bit key security using RC4 encryption
  • Adaptive Dynamic Polling
    Enables a more reliable wireless link in noisy environments
  • Protocol Filtering for bridged protocol
    Filters traffic according to protocol
  • Transparent VLAN tagging
    Will pass compliant Virtual LAN addresses, therefore operates as a standard connection
  • Continuous Signal Quality Monitoring
    Can test RF signal level, noise level and signal quality using a built in remote Point-to-Point testing feature.
  • Remote Wireless Link Analysis
    Can determine the performance of the connection via remote analysis from a single location.
  • Low Cost Solution relative to regulated Frequency Products
    Low cost, reliable - more economically viable than a regulated frequency product solution
  • No Governmental Frequency Licensing required
    The Point-to-Point Radio Backbone Kit operates in the unlicensed 2.4 GHz Radio Frequency Band.
  • Factory Pre-Configured for Network Bridge Operation
    Enables users to easily, quickly, and economically install a wireless LAN bridge between two locations.
  • Wide coverage range of up to 6 miles
  • IEEE 802.11b compliant
    ORiNOCO is the worlds' most popular wireless LAN Technology Due to its superior receiver sensitivity (ears) and resilience to microwave interference ORiNOCO has proven to be the best 802.11b radio in the industry, providing unbeatable performance results in range and throughput.

 

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