Linksys High Gain Antennas Reviewed
- Thread starter azazel1024
- Start date
azazel1024
Very Senior Member
On second, still can't stream Netflix :-(
red_pope
Regular Contributor
I'm not a WiFi expert, but doing good things for others, I call it, enhancing my IT skills. Recently my Son bought the same C8 model from TP-LINK that I have at home. Then I received hes phone call, asking me to help him out with the router.
I drove to hes property apartment and end up setting and configuring that router. As a Thank You, For me a good coffee and a piece of pie was sufficient from him.
red_pope
Regular Contributor
LOL,
Maybe ET speaks digital long range Communications.
In 2004 I did visited the Arecibo Observatory Radio Observatory and did interview the famous chupa cabra, he told me: "he is from Texas"! and then in 2005, the Mauna Loa Observatory in Hawaii. Please, Don't take rocks from the volcano home. It is bad yuyu! according to the Hawaiians.
sfx2000
Part of the Furniture
So going back to the article - and the cost of the kit...
The WRT1900ac is a fantastic radio already - it's probably one of the best in the AC1900 and higher classes - Linksys and Marvell did a fantastic job, at least on the V1 version - if they've release a higher gain set of antennas - that means they have done the testing against a specific design, and characterized matches and performance against an array of clients - and even there, the gains aren't going to be identical in the real world - it's a tweak/optimization towards specific use-cases, and all that testing and going back to the drawing board costs money - which justifies the cost of the kit.
Most folks won't benefit from the kit, which again justifies the cost - weeding out those who "might try it, just in case", and find out it doesn't do much for cases outside of those that engineering has tested/validated against.
The WRT1900ac is a fantastic radio already - it's probably one of the best in the AC1900 and higher classes - Linksys and Marvell did a fantastic job, at least on the V1 version - if they've release a higher gain set of antennas - that means they have done the testing against a specific design, and characterized matches and performance against an array of clients - and even there, the gains aren't going to be identical in the real world - it's a tweak/optimization towards specific use-cases, and all that testing and going back to the drawing board costs money - which justifies the cost of the kit.
Most folks won't benefit from the kit, which again justifies the cost - weeding out those who "might try it, just in case", and find out it doesn't do much for cases outside of those that engineering has tested/validated against.
azazel1024
Very Senior Member
sfx2000, I'll just have to agree to disagree. I see where you are coming from and everything you say is absolutely correct. I just think that the edge cases are less edge than you seem to indicate. Plenty of people on there and else where have mentioned adding higher gain rubber ducks on their routers and greatly improved wifi within their house. I've tested a bunch of setups and I generally see improved Wifi, especially in 5GHz. I am sure there are PLENTY of setups where it would make it worse. There might even be setups where someone thinks they've improved things, but most clients are actually suffering, except maybe it improved things in the really bad spots, which is what they needed and some performance being sacrafied in areas where things were fine is okay.
Overlapping channels or abutting channels can be a big problem. Especially in areas where there are a lot of basestations, business/enterprise/urban/dense suburban are probably all not good places for higher gain antennas. Then again, if you are restricting to 5GHz operation or primarily 5GHz operation focused, because of the poorer penetration, higher gain antennas might be very viable in most of those setups.
It is all about designing the entire setup to use what you have. Have higher gain antennas? You probably need to reduce basestation density to prevent interference gain.
My setup is fairly linear and I have no nearby neighbors to produce meaningful interference. I have my router on one side of my house, and AP close to the other side of my house a floor up and on non-overlapping channels and I have an outdoor AP on my garage the furthest from my router on the same channels as my router. It is almost a straight line rather than a triangle for the basestation setup. So the levels of interference each one can produce in the other is minimal at best with received signal levels generally being 40-50dB lower cochannel between the basestations that could interfere with each other. So a couple dB more gain could be good. In my case with lots of testing, including running wireless clients on the adjacent APs to generate potential noise, I found that going from 3 to 5dBi on my Archer C8 and 5 to 7dBi on my Archer C5 and WDR3600 all produced meaningful levels of 5GHz increased performance. 2.4GHz has been minimal across all of them, but there are slightly gains at long to extreme range on the order of 5% or so. 5GHz sees some pretty good increases generally in the 20% range on the 11ac basestations at most distances and the 11n sees those kind of gains at medium range and longer (nothing at short range).
Sure, most people are not going to test. Or do minimal testing. A lot of people are not going to have the setup where they might benefit from things. Some people are going to get total crap antennas. Since they are generally so cheap, I am going to keep buying one up (~+2dBi) antennas for my routers/APs and testing with them whenever I get a new router to play with. Worst comes to worst I wasted maybe $10-15 and a couple of hours of my time.
Overlapping channels or abutting channels can be a big problem. Especially in areas where there are a lot of basestations, business/enterprise/urban/dense suburban are probably all not good places for higher gain antennas. Then again, if you are restricting to 5GHz operation or primarily 5GHz operation focused, because of the poorer penetration, higher gain antennas might be very viable in most of those setups.
It is all about designing the entire setup to use what you have. Have higher gain antennas? You probably need to reduce basestation density to prevent interference gain.
My setup is fairly linear and I have no nearby neighbors to produce meaningful interference. I have my router on one side of my house, and AP close to the other side of my house a floor up and on non-overlapping channels and I have an outdoor AP on my garage the furthest from my router on the same channels as my router. It is almost a straight line rather than a triangle for the basestation setup. So the levels of interference each one can produce in the other is minimal at best with received signal levels generally being 40-50dB lower cochannel between the basestations that could interfere with each other. So a couple dB more gain could be good. In my case with lots of testing, including running wireless clients on the adjacent APs to generate potential noise, I found that going from 3 to 5dBi on my Archer C8 and 5 to 7dBi on my Archer C5 and WDR3600 all produced meaningful levels of 5GHz increased performance. 2.4GHz has been minimal across all of them, but there are slightly gains at long to extreme range on the order of 5% or so. 5GHz sees some pretty good increases generally in the 20% range on the 11ac basestations at most distances and the 11n sees those kind of gains at medium range and longer (nothing at short range).
Sure, most people are not going to test. Or do minimal testing. A lot of people are not going to have the setup where they might benefit from things. Some people are going to get total crap antennas. Since they are generally so cheap, I am going to keep buying one up (~+2dBi) antennas for my routers/APs and testing with them whenever I get a new router to play with. Worst comes to worst I wasted maybe $10-15 and a couple of hours of my time.
Some unrelated posts moved to new threads
http://www.snbforums.com/threads/re...er-5ghz-antenna-for-a-rt-n66-ac66-ac68.26410/
http://www.snbforums.com/threads/seeking-network-design-advice-for-home-remodel.26411/
http://www.snbforums.com/threads/re...er-5ghz-antenna-for-a-rt-n66-ac66-ac68.26410/
http://www.snbforums.com/threads/seeking-network-design-advice-for-home-remodel.26411/
azazel1024
Very Senior Member
Sure, if you are that far off. However, the move from 2-3 up to 6-9 sure can help boost your link budget a fair amount. That is generally more than enough to move up an MCS level.
So no, it won't generally help you establish a connection if you are well below minimum levels, but if you already have a strong enough signal for SOME kind of connection, it'll increase the throughput and stability of that connection. Which is generally the point. Every bit helps.
azazel1024
Very Senior Member
So, 4-6dB is insignificant when it can easily mean an increase of 1 or possibly 2 MCS levels.
Please wait while I mail you a 20-30% increase in wireless throughput.
If you cannot generate a stable link to begin with, 4-6dB probably isn't going to get you there. However, if you can generate a link, it is enough to substantially increase the performance of the link.
L&LD
Part of the Furniture
Once again, I agree with what you're saying. Not that stevech isn't correct also, but when you're more than just on the verge of connect / disconnect, a few extra dB's gives a much more responsive connection.
L&LD
Part of the Furniture
No, we're saying when the threshold is above pass-fail, it will offer a higher connection rate.
a wee bit. Intermittently.
4dB or so is a tiny fraction of the link budget.
L&LD
Part of the Furniture
Okay, so what is the total link budget?
link budget varies by location of course, but here's a generic example.
There are TWO link budgets in WiFi: Client-to-router and router-to-client. They differ due to the clients' usually having lower transmitter power.
Warning: Intro to RF system engineering 101 here. If you'd please take a moment to understand the basics, you can better sort reality from the abundant marketing B.S. and the under-informed users' euphoria (wireless is statistic vs. time. Things are always changing due to the situation, esp. with handhelds and mobiles, or in warehouses, etc.)
units: 0dBm = 1milliWatt = 0.001 Watt. Use of dBm is standard. It's a log scale due to the laws of physics where RF attenuates per the inverse square law, for distance.
Router-to-client
TX power varies by modulation mode and error rate, packet by packet. Can be 100mW in lowest rates of 11b, 11g; 11n's OFDM leads to lower power due to nature of OFDM and economics
TX power: 15dBm (~30mW) -- don't get suckered in on this by marketing or a phony GUI.
Typ. TX antenna gain (net of coax losses if any): 3dBi (dBi is antenna gain at boresight angle, relative to 0dBi for an ideal spherical radiator)
ERP (effective radiated power at boresight): +18dBm
Path length (router to client, ignoring obstacles): 100 ft.
Free space path loss, 2.4GHz, (attenuation): -70dB
Additional loss due for 2 drywall walls, 4dB per layer = 2 x 4Db = -8dB.
Additional loss due to trees, vegetation: 0dB
Additional loss due to occasional human body block (mostly, handhelds): -9dB
sum of the above: -70 - 8 - 9 = total path loss (TPL) = 87dB
signal level at client's antenna: ERP - TPL = +18 - 87 = -69dBm
Client receiver antenna gain (net of coax losses), at boresight: 2dBi (or less for handhelds)
Received signal level (RSL): -69 + 2 = -67dBm.
Now lookup vendor specs for achievable modulation rate (burst frame bps) for -67dBm. And what mode the radio firmware chooses to use at -67dBm. Say, 802.11n at x bps burst rate.
Add benefit of post-detection gain based on what modulation mode and MIMO/SIMO mode: about 4-6dB average. Add that.
-67 + 5dB = -62dBm (now we're getting idealistic about adding based on assumed goodness in the receiver design).
We wind up with -62dBm RSL.
(The burst rate bits per second per IEEE 802.11 frame. X percent of those bits are NOT useful data bits--- they are "coding", forward error correction bits. And this varies by frame by client by conditions, etc.
Now get the net throughput at the IP layer (useful data rate) by multiplying the burst rate by about 0.6). Because of coding, half-duplexing 802.11, etc.
So the 4dB improvement in antenna gain is a nit.
Margins and reserves...
The RSL needs to be at least 10 dB more than you want, for some desired average throughput. This 10dB allows for fading and increased path losses for obstacles.
And if you use directional antennas, you have the off-boresight gain issue to cope with. Unless you use a big omni stick which has a squished doughnut radiation pattern. That fails in a multi-story house on the Z axis.
There are TWO link budgets in WiFi: Client-to-router and router-to-client. They differ due to the clients' usually having lower transmitter power.
Warning: Intro to RF system engineering 101 here. If you'd please take a moment to understand the basics, you can better sort reality from the abundant marketing B.S. and the under-informed users' euphoria (wireless is statistic vs. time. Things are always changing due to the situation, esp. with handhelds and mobiles, or in warehouses, etc.)
units: 0dBm = 1milliWatt = 0.001 Watt. Use of dBm is standard. It's a log scale due to the laws of physics where RF attenuates per the inverse square law, for distance.
Router-to-client
TX power varies by modulation mode and error rate, packet by packet. Can be 100mW in lowest rates of 11b, 11g; 11n's OFDM leads to lower power due to nature of OFDM and economics
TX power: 15dBm (~30mW) -- don't get suckered in on this by marketing or a phony GUI.
Typ. TX antenna gain (net of coax losses if any): 3dBi (dBi is antenna gain at boresight angle, relative to 0dBi for an ideal spherical radiator)
ERP (effective radiated power at boresight): +18dBm
Path length (router to client, ignoring obstacles): 100 ft.
Free space path loss, 2.4GHz, (attenuation): -70dB
Additional loss due for 2 drywall walls, 4dB per layer = 2 x 4Db = -8dB.
Additional loss due to trees, vegetation: 0dB
Additional loss due to occasional human body block (mostly, handhelds): -9dB
sum of the above: -70 - 8 - 9 = total path loss (TPL) = 87dB
signal level at client's antenna: ERP - TPL = +18 - 87 = -69dBm
Client receiver antenna gain (net of coax losses), at boresight: 2dBi (or less for handhelds)
Received signal level (RSL): -69 + 2 = -67dBm.
Now lookup vendor specs for achievable modulation rate (burst frame bps) for -67dBm. And what mode the radio firmware chooses to use at -67dBm. Say, 802.11n at x bps burst rate.
Add benefit of post-detection gain based on what modulation mode and MIMO/SIMO mode: about 4-6dB average. Add that.
-67 + 5dB = -62dBm (now we're getting idealistic about adding based on assumed goodness in the receiver design).
We wind up with -62dBm RSL.
(The burst rate bits per second per IEEE 802.11 frame. X percent of those bits are NOT useful data bits--- they are "coding", forward error correction bits. And this varies by frame by client by conditions, etc.
Now get the net throughput at the IP layer (useful data rate) by multiplying the burst rate by about 0.6). Because of coding, half-duplexing 802.11, etc.
So the 4dB improvement in antenna gain is a nit.
Margins and reserves...
The RSL needs to be at least 10 dB more than you want, for some desired average throughput. This 10dB allows for fading and increased path losses for obstacles.
And if you use directional antennas, you have the off-boresight gain issue to cope with. Unless you use a big omni stick which has a squished doughnut radiation pattern. That fails in a multi-story house on the Z axis.
sfx2000
Part of the Furniture
Reposting here... since the original got rat-holed into an ASUS sub-forum...
===========
My final thoughts on Hi-Gain antennas and the like...
Hi-Gain antenna's generally don't work..
TL;DR - Science and Physics win!
Here's the reason - everyone is primarily client focused - in other words, if one increases power/gain on the AP, the clients will be better off... sometimes this might work, but testing here, and other sites, generally proves that this ain't true...
We need to be more than just client focused when looking at Tx power and Antenna Gain - an AP is one of many in the WLAN, and, folks know that when running tools like InSSIDer and similar ilk, that a crowed network is a noisy network - and this affects the AP as well as the associated clients.
When a client is transmitting, it's against the background of other noise in the channel - both members of the WLAN, as well as adjacent networks on the same channel (or slightly overlapping channels) - the AP is fighting the same problem, receiving the Tx bursts from the clients...
When we look at the Link - all things are relative - in CDMA 2G speak, we used to call it Ec/Io - or Correlated Signal over Noise - and this is a relative measurement, that's why it is related in Decibels, and not as a hard, fixed value like milliwatts, pascals, etc...
Since this is a relative value - it becomes easy to explain why higher gain antenna's generally don't work very well - they increase the levels of the associated clients, but they also increase the noise of the adjacent WLAN's along with jammers in close channels - so it all becomes relative - and it's generally a net-zero improvement at best.
Where high-gain antenna's can help - we can leverage into the tighter beam patterns afforded by High-Gain antennas and put interfering AP's and Clients into the null of the pattern - this is useful in tall-buildings, where jammers tend to be above and below, but this for many is an edge case... in a typical suburban house in the US, there is no gain, and a possible loss in the event of a house being more than a single floor.
Now going back to 3rd party antennas - those you can find on eBay or Alibaba - my recommendation is stay away from them - here's the reasons why...
In a radio - we do the basic RF modulation - and then we send it over to a power amplifier - this path is controlled by the designer and does not change - from the PA to the antenna - we try very hard to get the right impedance match to the antenna, because it is what converts the conducted to radiated energy - so the entire path is taken into consideration - including ensuring that the radiator has the correct match, and that even with the circuit board traces to the connector to the Reverse SMA on the outside of the router. A mismatch on the Tx side usually results in noise reflected back into the receiver (SWR impact), or lost energy, which is converted to heat...
On the receive side - from the antenna, we go into a low-noise amp - and a mismatch there will generally either reduce the signal, which is never good, or cause saturation and distortion - which is great if your a rock-star guitar player, but not if you're an RF engineer - as will cause issues downstream from the LNA into the baseband, which will not be able to demodulate those saturated/distorted signals...
So again, not a win for big antennas, eh?
End of day - WiFi has a designed link-balance that is pretty much vendor independent - and from there, rate decisions are made - there's a fair amount of "Kentucky windage" to ensure that Tx/Rx levels are fair/balanced, so accept that coverage is what coverage is from vendor to vendor - some do it better than others
Which makes the most important factor of WiFi - planning - put the AP where the people are, and accept that it's not going to get much better..
That being said - there are ways to improve things - AC1900 class routers generally use 3 radio chains, some use 4 - those extra RF chains help quite a bit, and that gain cuts both ways - additionally, the chipsets, using MIMO, and additional features like STBC and LDPC's, increase coding gain, and reduce internal noise - and a 3*3:3 AP is always operating in that mode - even with a single stream client... MIMO rocks, trust me... it's all about coding gain and signal recovery against the background noise.
So - stop tweaking Tx power, it doesn't help - high power AP's generally don't help because they make the link imbalanced, and big antennas amplify everything...
This is probably worth of a blog post on the external site...
sfx
===========
===========
My final thoughts on Hi-Gain antennas and the like...
Hi-Gain antenna's generally don't work..
TL;DR - Science and Physics win!
Here's the reason - everyone is primarily client focused - in other words, if one increases power/gain on the AP, the clients will be better off... sometimes this might work, but testing here, and other sites, generally proves that this ain't true...
We need to be more than just client focused when looking at Tx power and Antenna Gain - an AP is one of many in the WLAN, and, folks know that when running tools like InSSIDer and similar ilk, that a crowed network is a noisy network - and this affects the AP as well as the associated clients.
When a client is transmitting, it's against the background of other noise in the channel - both members of the WLAN, as well as adjacent networks on the same channel (or slightly overlapping channels) - the AP is fighting the same problem, receiving the Tx bursts from the clients...
When we look at the Link - all things are relative - in CDMA 2G speak, we used to call it Ec/Io - or Correlated Signal over Noise - and this is a relative measurement, that's why it is related in Decibels, and not as a hard, fixed value like milliwatts, pascals, etc...
Since this is a relative value - it becomes easy to explain why higher gain antenna's generally don't work very well - they increase the levels of the associated clients, but they also increase the noise of the adjacent WLAN's along with jammers in close channels - so it all becomes relative - and it's generally a net-zero improvement at best.
Where high-gain antenna's can help - we can leverage into the tighter beam patterns afforded by High-Gain antennas and put interfering AP's and Clients into the null of the pattern - this is useful in tall-buildings, where jammers tend to be above and below, but this for many is an edge case... in a typical suburban house in the US, there is no gain, and a possible loss in the event of a house being more than a single floor.
Now going back to 3rd party antennas - those you can find on eBay or Alibaba - my recommendation is stay away from them - here's the reasons why...
In a radio - we do the basic RF modulation - and then we send it over to a power amplifier - this path is controlled by the designer and does not change - from the PA to the antenna - we try very hard to get the right impedance match to the antenna, because it is what converts the conducted to radiated energy - so the entire path is taken into consideration - including ensuring that the radiator has the correct match, and that even with the circuit board traces to the connector to the Reverse SMA on the outside of the router. A mismatch on the Tx side usually results in noise reflected back into the receiver (SWR impact), or lost energy, which is converted to heat...
On the receive side - from the antenna, we go into a low-noise amp - and a mismatch there will generally either reduce the signal, which is never good, or cause saturation and distortion - which is great if your a rock-star guitar player, but not if you're an RF engineer - as will cause issues downstream from the LNA into the baseband, which will not be able to demodulate those saturated/distorted signals...
So again, not a win for big antennas, eh?
End of day - WiFi has a designed link-balance that is pretty much vendor independent - and from there, rate decisions are made - there's a fair amount of "Kentucky windage" to ensure that Tx/Rx levels are fair/balanced, so accept that coverage is what coverage is from vendor to vendor - some do it better than others
Which makes the most important factor of WiFi - planning - put the AP where the people are, and accept that it's not going to get much better..
That being said - there are ways to improve things - AC1900 class routers generally use 3 radio chains, some use 4 - those extra RF chains help quite a bit, and that gain cuts both ways - additionally, the chipsets, using MIMO, and additional features like STBC and LDPC's, increase coding gain, and reduce internal noise - and a 3*3:3 AP is always operating in that mode - even with a single stream client... MIMO rocks, trust me... it's all about coding gain and signal recovery against the background noise.
So - stop tweaking Tx power, it doesn't help - high power AP's generally don't help because they make the link imbalanced, and big antennas amplify everything...
This is probably worth of a blog post on the external site...
sfx
===========
sfx2000
Part of the Furniture
Actually, there is only one - a particular AP to STA link - but in our environment, there are many clients, but each one has to work with it's own link budget...
Yep...
OFDM/OFDMA has coding gain in it's favor, and when working an RF plan, it's a way to cheat things perhaps compared to DSS - one carrier with many symbols vs. many carriers with one symbol each...
Toss MIMO into the picture, symbol repetition helps out a bunch... and clients can use MRC to recover symbols (bits) that would be lost in the noise...
Most antenna's/antennae are not 'perfect' radiators - they've got some peaks and nulls - for most though, again, a perfect antenna as SteveCH suggests, radiates 100 percent 360 by 360 - in the real world, it don't...
Oddly enough for handsets - at 2.4GHz, with PIFA's and patches, we try to get there for 2.4GHz, not for WiFi but for Bluetooth in the hands free case.
So handsets are in some ways, horrible clients for home WLAN's, as these are not targets - it's the handset in your pocket attaching to the handsfree kit in your car, or the bluetooth headset...
The path losses that Steve mentions - they are a bit frequency dependent - body loss in the cellular space (head loss, etc) is typically figured as 4dB at 850MHz, 6dB at 1900MHz - when you get to 2.4GHz, remember, this is the waterhole, and we're mostly bags of water, so 9dB is is reasonable...
You forgot the PHY enhancements - MIMO and additional RF chains brings a significant amount of gain toss on top of the analog domain, sometimes up to 6dB...
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