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Professional Wireless Products
There is an abundance of equipment on the market for long distance, point-to-point (P2P) links. Most of this equipment is ready to go right out of the box, only the antenna cables need to be attached and sealed. When thinking about a long distance link, there are three main factors to consider: total link distance, uptime requirements, and of course, link speed requirements.
Most of the commonly available commercial products for longer range links now use OFDM technology and operate in the 5.8 GHz ISM band. There are some products available that use open standards, but most use a proprietary protocol of some sort. This does mean that in order to form a link, the radios on both sides will have to be from the same manufacturer. For mission critical links it is a good idea to choose a system that uses the identical equipment on both sides of the link. This way only one spare unit needs to be stocked, and if need be, can replace either side of the link. There are some good products on the market that use different equipment at either end of a link. These can be used in a network as long as it is done with care, or else spares will need to be available in both kinds of radios.
This is not meant to be a sales pitch for any radio, or complaints about them either. These are just some notes that have come from more then five years of field experience all over the world with unlicensed commercial products. There is unfortunately no way to review every product, so some favorites are listed below.
Redline first came to market with its AN-50 line of products. This was the first point-to-point product available with data rates above 50 Mbps that small operators could actually afford. They only use 20 MHz of spectrum per channel. There are three different models available in their AN-50 line. All three have the same basic feature sets, only the total bandwidth changes. The standard model has 36 Mbps throughput, the economy model has 18 Mbps, and the full version has 54 Mbps. The bandwidth controls are software upgradeable and can be added into the system as the demand for bandwidth increases.
Redline radios consist of an indoor unit, an outdoor unit, and an antenna. The indoor unit fits in a standard 19 inch rack, and occupies 1U. The outdoor unit mounts on the same bracket that holds the antenna in place. This outdoor unit is the actual radio. The two units are linked by a coax interface cable. Beldon RG6 or RG11 cable is used for this interface cable. This is the same cable used for satellite TV installations. It is inexpensive, easy to find, and eliminates the need for expensive low loss cable, like the Times Microwave LMR series or Andrew Corporation Heliax. Also, keeping the radio mounted so close to the antenna keeps the cable related loss to an absolute minimum.
There are two features to note on the Redline radios. The first is the General Alignment Mode, which turns on a beeper that changes tone as the modulation technique changes. Faster beeping means a faster connection. This allows for a much easier alignment as the link can be mostly aligned by the tones alone. Only a final tuning will be needed, and a graphical Windows application is available to help with this. The other feature is a Test button. Whenever radio changes are made but are not sure to be correct, pressing the test button instead of the Save button will make the new changes active for five minutes. After five minutes, the configuration reverts back to the setting before the test button was pushed. This allows the changes to be tried out, and if things don't work out and the link goes down, the link will come back after five minutes. Once the changes have been tried out, simply confirm the new settings in the configuration, and press the save button instead of the test button.
Redline has other models available. The AN-30 has four T1/E1 ports, in addition to a 30 Mbps Ethernet connection. The AN-100 follows the 802.16a standard, and the upcoming RedMax promises WiMax compliance.
More information: Redline Communications
One of the biggest advantages of working with Alvarion products is Alvarion's very well established worldwide distribution network. They also have one of the largest worldwide market shares for all kinds of wireless Internet connectivity hardware. There are distributors and resellers within most regions. For longer distance links there are two products of interest: The VL series, and the Link Blaster.
While the VL series is actually a point-to-multipoint system, a single client radio connecting to a single access point will function just fine for a point-topoint link. The only thing that should be considered is using a more directional antenna at the access point, unless there is a future link planned that could connect to that access point. There are two speeds available for the VL series, 24 Mbps and 6 Mbps. Budget, uptime, and speed requirements will guide the decision between which CPE to use.
The Link Blaster looks and feels a lot like a Redline AN-50. That's because it is one. Very soon after the Redline AN-50 came on the market, an OEM agreement between the two companies was signed, and the Link Blaster was born. Although the indoor unit is in a different case, and the antennas are marked differently, the electronics inside the units are identical. The Link Blaster does cost more then a Redline; this money buys you a more rugged design and an additional level of support. In many cases, an Alvarion reseller may be closer and easier to ship product from then some Redline re-sellers. This will be something that will have to be locally researched. It may be worth the extra money to have a product that is locally available and supported.
Alvarion does have some 2.4 GHz point-to-point products available. Most of their product range in the 2.4 GHz ISM band uses frequency hopping spread spectrum (FHSS) and will create a lot of noise for local direct sequence spread spectrum (DSSS) on the same tower. If a DSSS based distribution system is being planned for, then a FHSS backhaul is not going to be an effective option.
More information: Alvarion
Rad Data Communications
The Rad Airmux product line is relatively new to the market, and has some great potential. The Airmux 200 is a 48 Mbps radio, uses CAT5 cable, and comes with one of the most friendly price tags of any commercial solution. The units are small and easy to handle on a tower. The downside that may be found is a lack of a local distribution system in the developing world. There are two models available within the Airmux line. One uses internal antennas, and the other uses external antennas.
Experience with Airmux radios in early 2005 shows there is an issue in the timing configurations. This only becomes apparent when the link distance is more then 12 miles, or 19 km. It doesn't matter which antennas are being used. Until this bug is fixed, these radios should only be used for links under 19 km. When that guide is followed these radios preform very well, especially for their price point.
More information: Rad Data Communications
Cisco wireless solutions have two big advantages to their credit. They have a very well established distribution, support, and training network throughout most of the world. There are distributors and resellers all over the place. This can be a big help when it comes time to procure equipment, and even more important if equipment breaks and needs replacing. The next big advantage is that for the most part, they use open standards. Most of their available equipment follows 802.11a/b/g standards.
Experience has shown that their web based configuration tools are not as easy to understand as those found in many other products, and the equipment tends to come with a price tag that makes other non-commercial, open standard solutions more viable.
More information: Cisco
There are many more solutions available on the market now, and more arriving all of the time. Good solutions are available from companies like Trango Broadband and Waverider Communications. When considering which solution to use, always remember the three main factors; distance, uptime and speed. Be sure to check and make sure that the radios operate in an unlicensed band where you are installing them.
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