Yo, Whats legal power in the wifi 2.4Ghz world

[D-Boy]

then why the hell, do they make a 600mW AP, if you only allowed to use a 100mW, and that 600MmW AP, u connect directly to the antenna, so its not alot of power lost there

 

[UnUnOctium]

Yea, Wimax sounds like a waaayyyy better option, but its only that cost :-(

It is, 1 wimax high site (can be placed where your current WUG highsites are) a much larger number of users. Multiple access is also not a problem with WiMAX (OFDMA) unlike WiFi (CSMA-CA) this allows much more efficient communications with greater throughput and possible users. Place a base station in high-density areas (WUGs each connect to a high-site, high-sites are already the base stations to high-density areas) and link them at your own accord (high-speed landline works great for this), you have effectively minimised the WUG to smaller groups instead of powerful transmissions over long distances in THE most commonly used/polluted band there is.

 

[UnUnOctium]

then why the hell, do they make a 600mW AP, if you only allowed to use a 100mW, and that 600MmW AP, u connect directly to the antenna, so its not alot of power lost there

For the same reason they make cars which can do 320 km/h where the maximum speed limit in most countries is 120 km/h. It's not legal to use it at max power, but some people don't care and are willing (or ignorant) of when it comes to the consequences.

 

[D-Boy]

can't the same be done with wifi? why is the range so crap beside the low power of wifi
Can't they make a super sensitive base station for long range laptop / pda's2.4ghz wifi clients?

 

[D-Boy]

For the same reason they make cars which can do 320 km/h where the maximum speed limit in most countries is 120 km/h. It's not legal to use it at max power, but some people don't care and are willing (or ignorant) of when it comes to the consequences.

Life suck....lol

 

[UnUnOctium]

can't the same be done with wifi? why is the range so crap beside the low power of wifi
Can't they make a super sensitive base station for long range laptop / pda's2.4ghz wifi clients?

Receiver sensitivity is a very important topic in microelectronic design, it's one figure that all manufacturers try to best. Wifi has a crap range because of power, both a good quality wimax and a good quality wifi receiver will have a receive sensitivity of around -100 to -120 dBm. If you put out wifi at 20 dBm, you only have 140 dBm of SNR at best [which you'll never achieve in practice], whereas with wimax, you'd probably have in excess of 150 dBm [same as never in practice] (depending on what transmit power icasa gives it, don't have the updated documents). Those 10 dBm can make all the difference. The problem isn't with power so much as the multiple access inefficiency and ubiquity of 2.4 (everything's there, from bluetooth to little SRDs).

 

[D-Boy]

Receiver sensitivity is a very important topic in microelectronic design, it's one figure that all manufacturers try to best. Wifi has a crap range because of power, both a good quality wimax and a good quality wifi receiver will have a receive sensitivity of around -100 to -120 dBm. If you put out wifi at 20 dBm, you only have 140 dBm of SNR at best [which you'll never achieve in practice], whereas with wimax, you'd probably have in excess of 150 dBm [same as never in practice] (depending on what transmit power icasa gives it, don't have the updated documents). Those 10 dBm can make all the difference. The problem isn't with power so much as the multiple access inefficiency and ubiquity of 2.4 (everything's there, from bluetooth to little SRDs).

I dont fully understand what you saying here, but is it because there is less noise in the wimax frequency spectrum so that's why wimax works better

 

[Tacet]

One thing about power output many people miss is that 2.4 is a SHARED band. Meaning that if you transmit 1W in the 2.4 band, you could easily mess up my Wifi link. Or my neighbours. One of the main reasons the power is legally capped on the 2.4 band is to limit interference for other people. The non-shared bands are all controlled, and each and every link should be registered with ICASA in order to manage interference. If an operator "owns" a part of the 38GHz band, and they pick up interference, it is either because their own planning is very bad (another transmitter on their own network), or because someone is transmitting illegally in their band. Either way, the problem can be resolved easily. In the 2.4 band, no one knows who is causing interference, and uncapping the power output would cause the noise floor of the band to rise significantly.

 

[UnUnOctium]

I dont fully understand what you saying here, but is it because there is less noise in the wimax frequency spectrum so that's why wimax works better

in a way, yes. post by Tacet summarises it very nicely. For WiMAX vs WiFi, you have to know the mathematical and technical workings of CSMA-CA vs OFDMA to know why it's just infinitely better.

 

[D-Boy]

hmmmm what about MIMO vs. WiMAX ?:wtf:

 

[Roman4604]

but is it because there is less noise in the wimax frequency spectrum so that's why wimax works better

That and the converse of what Tacet said about the capping of tx power in the 2.4 band.

Licensed freq like WiMax does not have these restrictions, if memory serves me right the 2.6 WiMax equip we last used was speced at ~25W tx output per sector. Thats like the difference between screaming* and whispering.

* Any association to other parties is purely coincidental

hmmmm what about MIMO vs. WiMAX ?:wtf:

Not comparible, MIMO is an antenna technology/architecture. Both WiMAX & WiFi can, and in many implementations, do use MIMO.

 

[D-Boy]

25W omf... that's heavy


Is MIMO compatible with G range ? I have no experience with MINO

 

[Roman4604]

Is MIMO compatible with G range ? I have no experience with MINO

If you're meaning 802.11g, dont think so. 11g pre-dates the widespead use of MIMO, so only newer 802.11n kit.

 

[D-Boy]

I dont understand what you mean, so If I have a MIMI AP's but my client device is a 802.11g, will that client be able to connect? and is it wise to have MIMO basestations for a WISP?

 

[Roman4604]

so If I have a MIMI AP's but my client device is a 802.11g, will that client be able to connect?

Yes it will (if AP set to mixed mode) just wont take advantage of MIMO like a 802.11n client would.

 

[D-Boy]

"just wont take advantage of MIMO like a 802.11n client would."

Why not? if it on mixed mode?

EDIT : I'm confussed....

will a 802.11n client take advantage of the AP, but at the same time the 802.11g will just be plain 54mbps, and both are connected to the AP..... if I'm correct?

 

[Tacet]

@ D-Boy, get your technologies straight. MIMO (multiple input, multiple output) means that the system has more than one antenna on both the transmitter side and on the receiver side. Using a few very clever techniques, this allows increased throughput. 802.11n supports MIMO, as does certain versions of the WCDMA family of specs. I'm not sure about WiMAX, but I suspect that some of the newer (maybe from E on, I'm not sure) uses it as well.

I suspect that no one here really knows the 802.11n spec well enough to comment properly on it. Depending on the spec it might still give better throughput when used with an 802.11g client than an 802.11g AP would, but I'm not sure if it does. But yes, in mixed mode it will be able to handle both 802.11n and 802.11g clients.

@Roman4604 - 25W is 43dBm. Was that the IF power or Tx power? 43dBm transmitted feels a bit much - not sure if that is legal anymore. I'm curious now, will read it up a bit.

 

[Roman4604]

@Roman4604 - 25W is 43dBm. Was that the IF power or Tx power? 43dBm transmitted feels a bit much - not sure if that is legal anymore. I'm curious now, will read it up a bit.

Not 100% sure, but as far as I remember tx power. Was told in answer to my question how I was able achieve 7Mbps from 11Km away non-LOS (over the horizon). Basically because of the juice each sector puts out, Alvarion BreezeMax 2500 BTS (802.16e).

 

[UnUnOctium]

@ D-Boy, get your technologies straight. MIMO (multiple input, multiple output) means that the system has more than one antenna on both the transmitter side and on the receiver side. Using a few very clever techniques, this allows increased throughput. 802.11n supports MIMO, as does certain versions of the WCDMA family of specs. I'm not sure about WiMAX, but I suspect that some of the newer (maybe from E on, I'm not sure) uses it as well.

I suspect that no one here really knows the 802.11n spec well enough to comment properly on it. Depending on the spec it might still give better throughput when used with an 802.11g client than an 802.11g AP would, but I'm not sure if it does. But yes, in mixed mode it will be able to handle both 802.11n and 802.11g clients.

@Roman4604 - 25W is 43dBm. Was that the IF power or Tx power? 43dBm transmitted feels a bit much - not sure if that is legal anymore. I'm curious now, will read it up a bit.

To clarify, WiMAX has had provisions for MIMO since the first .16 draft. They quite like 2x2 MIMO for mobility wimax due to small antenna size and 2x2 being the most efficient code (Alamouti).

I 'know my bit' when it comes to multi-carrier wireless Most 802.11n systems use a 2x2 or a 3x3 configuration (max allowed was 4x4 if i remember correctly). If you try and connect a .11n and a .11g device to a .11n router the .11n card will still maintain full speed while the .11g card will maintain its full speed. This is because MIMO in .11n is done using space-time block coding with TDMA, meaning that the antennae are exploited per user, per time, not for just space diversity (i.e. multiple, simultaneous transmissions to different users).

 

[Tacet]

To clarify, WiMAX has had provisions for MIMO since the first .16 draft. They quite like 2x2 MIMO for mobility wimax due to small antenna size and 2x2 being the most efficient code (Alamouti).

I 'know my bit' when it comes to multi-carrier wireless Most 802.11n systems use a 2x2 or a 3x3 configuration (max allowed was 4x4 if i remember correctly). If you try and connect a .11n and a .11g device to a .11n router the .11n card will still maintain full speed while the .11g card will maintain its full speed. This is because MIMO in .11n is done using space-time block coding with TDMA, meaning that the antennae are exploited per user, per time, not for just space diversity (i.e. multiple, simultaneous transmissions to different users).

I think I'll take your word on this one. Seems like you're a bit better informed on 802.11 than I am.