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Why no 802.11ac Airport Express?
- Thread starter tanker5
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Not exactly sure whether it's actually possible to have the features of 802.11ac in the form factor of the Airport Express as it requires more space for MIMO antennas. This is one of the reasons for the new vertical design with the just announced 2013 Airport Extreme and Time Capsule.
Looking at the teardown on ifixit.com I'm not sure that's true. The antenna array is just at the very top. I think the "marketing spin" is that by elevating the antenna you'll get better Wi-Fi performance, but I don't see any reason the routing guts couldn't be put into a box about the size of the current Express.
Yes, ac can be implemented in the Express form factor, you just won't have beam forming. You can implement ac with fewer antennas, it simply transmits and receives in a conventional 360 deg pattern. Older wifi standards, part. g and n, had stipulations for manufacturers to implement more or less antennas. Client side ac radios will obviously be much more compact with fewer antennas as are current client wifi radios.
Its not marketing spin. Yes you can build it in a flat box like the prev Extreme or TC, but beam forming could be severely impeded by surface clutter, table surface, etc. Theres an actual science to beam forming, look up phased array. Apple could have implement an array of exposed antenna elements but they've always preferred to conceal them.
http://en.wikipedia.org/wiki/Phased_array
OK "Spin" maybe was harsh
but based on the teardown they could probably build an AC Express in the current Express casing, and it would work fine if properly positioned (or maybe it could come with a monopole stand to elevate it a bit)OK "Spin" maybe was harsh
Yes, and it will perform ac networking just fine, it just won't perform beam forming. Beam forming is not required for ac, just as client side ac radios will not do so, simply needed for directed energy transmissions which is best provided through a primary routing device.
Relying on the customer to have to properly position the device optimally would leave them open to another "you are holding it wrong" debacle
Yes, and it will perform ac networking just fine, it just won't perform beam forming. Beam forming is not required for ac, just as client side ac radios will not do so, simply needed for directed energy transmissions which is best provided through a primary routing device.
Relying on the customer to have to properly position the device optimally would leave them open to another "you are holding it wrong" debacle
Why no beam forming? I'm mobile ATM so can't review the Ifixit tear down easily, but it appeared that the entire antenna array is in a slim board on top of the new Extreme. The tall canister is just for the hard drive & circuitry (and to elevate said antenna array).
The elevated clearance required to most efficiently direct the transmissions.
I work for a major wireless hardware manufacturer. The trouble with the AC chipsets is heat. The Airport design form factor has nothing to do with the antenna array or beamforming, and everything to do with heat dissipation. They turned the entire thing into a heatsink. You'll see SOHO WAPs (Apple, belkin, netgear etc) adopting janky Al internal heatsinks, and enterprise (Cisco, Aruba, HP, etc) customizing the chassis and tweaking firmware to offset heat gains.
... but a lot of people also use the Express to extend the range of their network.
True, but the extra space for the antennas does help. Although it doesn't mean we need a tall router.
How is ac implemented in a phone that doesn't have space for several "tall" antennas and shouldn't the next iPhone have it too?
If it can be packed in a phone then Apple should be able to make a reasonable sized and priced ($99) Express.
I gather that the height/shape is helpful for beamforming, which is done on the router end only.
How does that help uploading from the connected device (laptop, phone, ...)? That would mean an asymmetrical connection (ac from router but only n to the router???).
Beamforming directs the signal toward the device, so if you're say 50 ft due east from your base station, beamforming makes the signal stronger to the east than to the north & south. That's what it sounds like from the wikipedia article anyway
I'm no expert.Beamforming directs the signal toward the device, so if you're say 50 ft due east from your base station, beamforming makes the signal stronger to the east than to the north & south. That's what it sounds like from the wikipedia article anyway
I understand but what I'm asking is what about the beam (data) from the device to the router. If there is no beam forming from device to router then there is asymmetrical (no ac??) communication.
Again, I'm no expert - but the wiki indicates that beamforming can improve both transmission and reception, so it's plausible that beam forming only on one end could help sending data more efficiently and receiving it more efficiently. Beamforming doesn't change the nature of the signal (I.e. change an n signal to an ac), it's just a means of improving signal performance to a specific area as compared to omnidirectional antennas.
Im no expert either but from my understanding that is not the way 2 way radio communication works. Here are 2 analogies and anyone with radio engineering expertise feel free to correct me.
1) You seem to be implying/understanding that when a beam forming transmitter (ac router) sends a signal it [metaphor] lays a water pipe that the receiver (phone/laptop) can then use to same pipe to send water back.
2) My understanding is [metaphor] in a conventional radio (b,g and n router) works like a circular misting lawn sprinkler sending out a fine even mist in all directions but not too far. The receiver (phone/laptop) has a cup that catches whatever fine mist of water it happens to be near. Then the phone/laptop has its own circular misting lawn sprinkler that is sends the water back and the router catches it in its cup.
In ac beam forming the router locates the (phone/laptop) and sprays the full jet of water at it. This way most of the volume (amount of data) and pressure (distance) lands in the receiver's cup. Now the phone/laptop must send the water back. If its ac then if must be able to locate and spray the full jet of water at the routers cup. If not then it would just be sending a fine mist of water in all directions which would mean low volume and decreased range (asymmetrical).
Having beam forming on only one end of the transmission path does indeed benefit data transmission in both directions. Beam forming is essentially increasing the gain of one antenna (at the router) in the direction of the intended remote device. Due to the reciprocity theory, this gain -with associated increase in Signal-to-Noise ratio - will be equally evident in both directions.
Now if the remote device also happened to have active beam forming capability, then the channel would achieve even greater gain and Signal-to-Noise ratio. But having it at only one end does work in both directions.
For example, assume that beam forming achieves a 6 dB gain. If only the router has beam forming, the channel will have 6 dB higher gain for transmission in both directions. If both the router and the remote device have active beam forming, then the channel would have 12 dB higher gain for transmission in both directions.
Note, however, that based on what is contained in Apple's specs for the new ac Airport Extreme, beam forming only occurs when the router detects a remote device with ac capability. So it apparently isn't active with b,g,n remote devices even though it would offer increased signal strength. I'm not sure why this limitation exists. Perhaps someone with more specific knowledge of networking can weigh in with a more detailed explanation.
Now if the remote device also happened to have active beam forming capability, then the channel would achieve even greater gain and Signal-to-Noise ratio. But having it at only one end does work in both directions.
For example, assume that beam forming achieves a 6 dB gain. If only the router has beam forming, the channel will have 6 dB higher gain for transmission in both directions. If both the router and the remote device have active beam forming, then the channel would have 12 dB higher gain for transmission in both directions.
Note, however, that based on what is contained in Apple's specs for the new ac Airport Extreme, beam forming only occurs when the router detects a remote device with ac capability. So it apparently isn't active with b,g,n remote devices even though it would offer increased signal strength. I'm not sure why this limitation exists. Perhaps someone with more specific knowledge of networking can weigh in with a more detailed explanation.
Hopefully they will soon... we need another access point in the garage (we already have 2 extremes and a time capsule all new gen) which is somehow not enough... I hope they sort out the antenna and bring one out soon in fact I am sure apple will very quietly do this one weekend before the end of the year (I hope).