Wireless Explained

 
On this page, I will try and provide some solid numbers/facts concerning Wireless (and other device speeds)
 
The information below is a compilation of facts and things I felt relevent and is simply sectioned off
 
I tried to average these out to make it simple.
The last column are my average results from my personal tests (shown in other tables below this one)
My test column is using results from my DV3500nr laptop
 

 Band/Interface

MAX Speed  Frequencies available for use My AVG REAL Speed (~25ft with obstacles from desktop to laptop with wifi)
 A  54 mbps 5 ghz  20 mbps 
 B  11 mbps 2.4 ghz  4 mbps / .5 MBs 
 G  54 mbps / 6.75 MB/s  2.4 ghz  20 to 24 mbps / 2.5 to 3 MBs 
N  150 mbps (20mhz) 2.4 ghz / 5 ghz 

4.5 MB/s 

(9 MB/s No Obstacles)

IDE / PATA 133 MB/s     
Esata   300 MB/s    
 SATA 7200 16mb cache 3 gb/s 300 MB/s  
 SATA 5400    
 USB 2.0  480 mbps 60 MB/s   ~ 25 MBs
 100 Ethernet  100 mbps 12 MB/s    11 MBs
 1000 Ethernet  1000 mbps 120 MB/s  

 Dependent on many things like, processor and HDD Type/Speed

~40 to 100 MB/s

7200rpm 16mb Cache 3 gb/s

See Table Below

 AVG Cable Internet 12 mbps / 1.5 MBs Down  
 AVG DSL  1.5 mbps down    
 
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This graph below is for my personal tests in my home using a 5GB single file transfer
 
I have found my home to be a very decent place as far as wireless range is concerned.
I have set up wireless in a number of homes and some places it goes throughout the home pretty good and in others it has trouble getting into the next room with a strong signal.
There is only a couple other wireless networks that I can detect from my neighbors around me.
 
The only frequency tested was on the 2.4ghz freq.
The tests were done with WPA2 encryption
This test was done with 3 computers connected to a network - 1 wired and 2 wireless (both with N capability).
 
I initially did the tests from the wired pc to the wireless pc but noticed there was a significant difference when I reversed this.
So look for the lables Lap and Desk to tell the difference.
 
During the tests only 1 network device was presenting a network load (no updates, internet browsing, etc.) 
 
These tests were each done a few times to get an average.
After 50 ft, I was in my backyard.
The router is in the very front of the house on the first floor with nearly a clear shot through the living room, through the sun room and into the large backyard.
The distance I tested with obstructions was from next to the router to 25 ft away (kitchen to living room with 2 large freezers, 1 large fridge and lots of cabinetry and a closet)
I noticed that when outside, I found a +/- 30 ft difference in the 1 MB/s test with both the G and N Signals
 
I chose 1 MBs for the distance test because your AVG high speed cable internet gets you around 1-1.5 MBs tops.
So if my neighbor was at that distance or close to it, he might get a pretty good internet speed from me.
 
Also, I have read about the questionable accuracy of the windows speed guage shown in the details of a file copy.
I used an alternate program called Bandwidth Meter and got similar results.
The main difference was that with Bandwidth Meter, I could get instantaneous readings and with the Windows reading, it averaged it out
  
 
Router

 Band/Laptop

AVG Speed @ 2ft  AVG Speed @ 25ft (No Obstacles) AVG Speed @ 25ft (with obstacles) Furthest distance maintaining 1 MB/s
WRT54GS   G / Sams N210 3.4 MB/s 3.3 MB/s  3.2 MB/s 120 ft
WRT54GS  G / DV3500nr   3 MB/s 2.9 MB/s  2.9 MB/s  120 ft 
Linksys E2000 Mixed Mode Desk to Lap  G,N / DV3500nr  9.7 MB/s  9 MB/s 4 to 5 MB/s  120 ft 
 Linksys E2000 Mixed Mode Lap to Desk   G,N / DV3500nr 5.9 MB/s  5.5 MB/s  3 MB/s 120 ft
Linksys E2000 Mixed Mode Desk to Lap  G, N / Sams N210  5.9 MB/s  4.5 MB/s   3.7 MB/s 120 ft 
 Linksys E2000 Mixed Mode Lap to Desk G, N / Sams N210   4.1 MB/s 3.3 MB/s  2.7 MB/s   
 
 
Notice that the distance of the 1 MB/s test is the same for all the tests!
This is what I experience in many people's homes when I install wireless or troubleshoot their wifi.
Whether it be G or N or Mixed or Not, I find that on AVERAGE, it makes no difference when Max range is concerned.
 
So, using 802.11n won't improve your WLAN range.
 802.11n can provide higher throughput at a given location than 802.11b/g and in that way turn a borderline-usable location into a happy web-surfing spot. But it won't get you a signal in that hard-to-reach bedroom on the top floor any better than an 802.11g router will.
However, a router with a better antenna (more expensive) may give you better range.
 
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Gigabit Ethernet Test 1
 
Single 5gig file transfer
Tested several times for validity
All Hard drives 75% Empty
E2000 Router, Cat 5e, ~6ft cable from computer to router
 
Computer  Hard Drive 
 Quad Core, Win 7, 4gb RAM Desktop

 Model - WD5000AAKS-65VOA

7200rpm 16mb cache, 3gb/s

 Core 2 Duo, Win Vista, 4gb RAM Laptop

Model - ST9500420AS 

7200rpm 16mb cache, 3gb/s

 
From Desktop to Laptop = 100 MB/s to 50 MB/s steady decrease
 
From Laptop to Desktop = 95 MB/s steady
 
Results - Evidently, the sustained write speed of the laptop is not as good as the desktop
 
Laptop                                                                                                            Desktop
                                                                 
 
 
Gigabit Ethernet Test 2
 
Single 5gig file transfer
Tested several times for validity
All Hard drives 75% Empty
E2000 Router, Cat 5e, ~6ft cable from computer to router
 
Computer  Hard Drive 

 Quad Core, Win 7, 4gb RAM Desktop

SAME as test 1

 Model - WD5000AAKS-65VOA

7200rpm 16mb cache, 3gb/s

SAME as test 1

 Core 2 Duo, Win 7, 3gb RAM Laptop

Model - ST9320423AS 

7200rpm 16mb cache, 3gb/s

 
From Desktop to Laptop = 22 MB/s steady
 
From Laptop to Desktop = 42 MB/s steady
 
Laptop                                                                                                        Desktop (SAME)
 
 
 
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As a side note, when it comes to watching a video from a networked PC, here are the average bitrates of a few types of video.
 
Please keep in mind that when it comes to your downloaded or re-encoded content, different encoding methods yield different bitrates and framerates and resolutions and dont forget the different types/sizes of audio which also impact it.
So its highly variable.
I based the Average MKV bitrates below on my collection taking an average of 1080 & 720 due to what I just mentioned above.
 
I recommend this program below for measuring the bitrate of your downloaded content:
 
Media  MAX Bitrate  AVG Bitrate (audio & Video)
 Commercial DVD  10 mbps 7 mbps 
SD TV  2-5 mbps 
HD TV   19 - 24 mbps
 Uncompressed Blu Ray 40 mbps vid / 54 mbps aud/vid   
AVG Re-encoded "BluRay Rip" HD Video (MKV ~18gb & 2.5hrs)   15.5 mbps 
AVG Re-encoded "BluRay Rip" HD Video (MKV ~10gb & 2hrs)    10 mbps
AVG Re-encoded "BluRay Rip" HD Video (MKV ~5gb & 1.5hrs)    6 mbps 
 
 
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Here is a calculator/converter for bits per sec.
 
HDD Speeds
 
-There is a difference in the Initial burst speed and the rest speed after that - 130 MB/s Burst vs AVG 60 MB/s (the Rest) for SATA 2 7200rpm
 
-It also depends on the type(s) of file(s) being transferred (Many small files or one large file), How full the disk is, the type of disk, how fragmented, anything else going on in the background...
 
Wireless Speeds

-According to the article noted toward the end of this page, the Max link rate in 20-MHz mode (explained below) is only 150 mbps (18 MB/s) (rather than the much-advertised 300 mbps (37 MB/s) which would be with the 40mhz signal in prime conditions).
I have also read that using the 40-MHz may actually hurt your throughput.

The Channel-bonding trick can provide a 10 to 20 Mbps throughput increase, but usually works best under strong signal conditions. As signal levels drop, using channel bonding becomes much less effective in providing a throughput boost.

 
-The range is highly affected by many things including the different types of equipment (both broadcasting and receiving), wifi interference and obstacles

-A wall may cause a 25%+ decrease in range

-more antennas (better router) can help boost range
 
-So you bought a gigabit router and you are not getting gigabit speeds. Remember that the slowest part of your network is the weekest link. One thing most people forget is that the RJ-45 (NIC, Ethernet) jack on both computers must be rated for gigabit - this would be the 1000 out of the 10/100/1000.
 
-Also, just because you buy a fancy new Wireless N router, unless you have a wireless N receiver on your laptop, you will still use wireless G.
 
-If you have wireless G devices connected to your network, the presence of these will slow down your throughput.
 
-Also, you can only use WPA2/AES Wireless Security (or no security at all) if you don't want to throw away lots of speed.
However, I have found in practice, that WPA2 - mixed or not - can cause connection problems for some devices (mostly in the slightly older category) in some networks. I tend to stick with WPA encryption when setting up Wireless Networks for my customers. I got tired of people calling me because their PC's would no longer connect for some mysterious reason when I let WPA2 in the mix.
 
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To get full 300mbps of N, you must have VERY ideal conditions:
-must be transmitting in full n mode (no G transmit)
-Little Interference
-Must use 40mhz operation (channel bonding)(greater risk of interference than 20mhz)
-better off on the 5ghz freq if using channel bonding to avoid 2.4ghz interference
 
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If the 2.4ghz frequency is having trouble transmitting in your area due to other 2.4ghz freq in the air, you can try broadcasting a 5ghz signal.
The downside is that the 5ghz signal does not transmit as far and has more trouble with walls and such.
 
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ABOUT CHANNEL BONDING:
 
A Wi-Fi’s channel is required to be 20MHz. Thus, just like the name says, a ‘double wide’ takes up 40MHz of radio room instead of the usual 20MHz. The
problem is that there’s only room for three 20MHz channels in 802.11b/g/n’s 2.4GHz radio spectrum. If you run out of Wi-Fi spectrum room, your overall
network throughput will decline. Even if you’re doing a good job of managing your network space, your available channels are likely to also be used by your
next-door neighbors’ Wi-Fi set-up.
 
The easiest way to dodge this potential problem, for now, is to use the higher 5GHz range. Far fewer people are currently using the 5GHz range. This will
change as more people switch over to 802.11n, but for now it’s the easiest way to use wide channels to increase your effective bandwidth without running into
interference. The one downside is that 5GHz has less range than 2.4GHz.

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Question: How Can the Range of a Wi-Fi Network Be Boosted?
 
You can boost the signal range of a Wi-Fi computer network in several ways:
 
-reposition your router (or access point) to avoid obstructions and radio interference. Both reduce the range of Wi-Fi network equipment. Common sources of
interference in residences include brick or plaster walls, microwave ovens, and cordless phones. Additionally, consider changing the Wi-Fi channel number on
your equipment to avoid interference.
 
-upgrade the antenna on your router (or access point). Wi-Fi antennas on some wireless base stations can be removed and replaced with more powerful ones.
 
-add another access point (or router). Large residences typically require no more than two APs, whereas businesses may employ dozens of APs. In a home, this
option requires connecting your primary wireless router (access point) to the second one with Ethernet cable; home wireless routers and/or APs don't normally
communicate with each other directly.
 
-add a Wi-Fi repeater. A wireless repeater is a stand-alone unit positioned within range of a wireless router (access point). Repeaters (sometimes called
"range expanders") serve as a two-way relay station for Wi-Fi signals. Clients too far away from the original router / AP can instead associate with the WLAN
through the repeater.
 
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Distance vs Throughput speed
 
A wireless signal may be able to be detected at a great distance, but whether that distant signal will be tolerable for use as far as consistant speed is a
different story. And when you add obstructions such as walls and other wireless intereference into the mix, you have even less distance/throughput.
 
Also, speed decreases when more than one person is using a wireless signal.

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Deconstructing the Technology
 
The 802.11n variant of Wi-Fi achieves its high through??put (typically four times that of 802.11g) in two ways. First, it uses MIMO (multiple input, multiple
output) antenna technology to transmit more data at a time. Intelligent antennas combine streams of data arriving at different times from multi??path signals
bouncing off walls, floors, and ceilings. Entry-level routers typically have two receiving and transmitting antennas; midrange and high-end models have three
of each.
 
Second, draft-n uses channel bonding: Instead of the 20-MHz-wide channels found in previous Wi-Fi standards, 802.11n can use 40-MHz-wide channels, which in
theory should double their data-carrying capacity.
 
Unfortunately, the limited bandwidth of the 2.4-GHz range means that just one 802.11n router using channel bonding will take up virtually the entire 2.4-GHz
spectrum, leaving no room for neighboring routers, and causing severe interference. For this reason, draft-2.0's so-called good-neighbor policies require
that routers ship in 20-MHz mode, and that, when in 40-MHz mode, they drop to 20-MHz operation if they sense nearby Wi-Fi nets or other 2.4-GHz devices. The
top link rate in 20-MHz mode is only 150 mbps (rather than the much-advertised 300 mbps); since many users are likely to be within range of other 2.4-GHz traffic, we ran our 2.4-GHz tests with 20-MHz channels.
 
More Bandwidth, Less Range
 
The 5-GHz frequency range, however, has much more bandwidth to play with and can support multiple 40-MHz channels. It's also relatively unused (802.11a
products appeared primarily in business environments), so interference is generally minimal to none. We therefore used 40-MHz channels in our 5-GHz testing
of the two routers that support 5-GHz operations.
 
Interestingly, even with twice as much channel bandwidth, speeds in our 5-GHz testing at close range did not double; on average, they rose about 20 percent.
But they were generally more consistent than the 2.4-GHz results, and throughput at close range never dropped below 40 mbps--well above the 25 mbps needed
for top-quality HDTV streaming.
 
The downside to 5-GHz: Its higher frequency doesn't allow it to cover as large an area as 2.4-GHz draft-n. But its range is still generally far better than
that of standard unenhanced 802.11g.
 
Another 5-GHz plus: While draft-n is backward-compatible with 802.11b and g gear in "mixed" 2.4-GHz mode, performance for n clients drops significantly on
networks when b or g clients are present. But with a dual-band router, you can put newer draft-n gear that supports 5 GHz on the fast track while maintaining
a slower 2.4-GHz network for older gear. We recommend a dual-band router if you need maximum performance for streaming media or networked storage--or if you
can't get a good Wi-Fi signal at all due to interference from neighbors' networks.
 
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I thought this source below was an excellent source of information concerning speeds of equipment as I did my research above to get some solid information:
I have copied it below in case the info is lost:
 
The theoretical speed rating of a given wired or wireless connection can be betrayed by a number of factors, from the overhead of the protocols involved to signal interference. Network data throughput is usually measured in megabits per second, which are an eighth of a megabyte per second. Disk speeds are typically cited in megabytes per second; here, I'll list both numbers to make it easier to compare disk and network throughput speeds.

SATA, or Serial ATA, has a theoretical maximum of 1200 Mbits/sec (150 MB/sec). However, existing hard drives can't even deliver data that fast; top disk output speeds are closer to 40 to 100 MB/sec, depending on whether the data is being read from the inside or outside of the disk platter, the disk spin speed, and other factors.

USB 2.0 has a theoretical maximum of 480 Mbits/sec (60 MB/sec). A USB hard drive is typically a standard ATA or SATA drive attached to a USB bridge chipset. The actual speed of the USB interface depends upon the performance of the chipset used as well as the performance of the computer the drive is attached to. That's because USB transfers most of the heavy lifting to the host computer's CPU.

USB has a faster theoretical maximum than Firewire 400 (400 Mbits/sec; 50 MB/sec), but Firewire 400 is actually much faster than USB because it uses smarter peer to peer interface hardware rather than pushing low level work onto the PC host's CPU as the simpler master to slave architecture of USB does.

On a Mac, Firewire is typically around twice as fast in real world transfer rates, with USB hitting around 18 MB/sec and Firewire reaching 35 MB/sec throughput. Windows' implementation of USB has historically been faster than Mac OS X's, with Windows' USB reaching throughput closer to 33MB/sec. That also explains why Firewire is more popular on the Mac than on the PC side; it's simply far more dramatically faster than USB on the Mac, while Firewire offers less of a noticeable boost in Windows. Macs also have Firewire Target Mode, which PC users lack. For more details on why USB is faster in Windows compared to the Mac, see the footnote: USB Performance in Windows vs Mac OS X at the end of this article.

Time Capsule doesn't use Firewire; it's USB only. There are two reasons for this. First, USB chipsets are cheaper than Firewire, because they do less (USB peripherals have less intelligence on board and transfer more work to the CPU). Second, Time Capsule and the AirPort Extreme are both designed as wireless network appliances, so the difference in performance between attached Firewire and USB drives typically wouldn't be noticeable. Test results presented in the next segment bear that out.

In reality, USB doesn't simply run at a given speed. The performance of a directly connected USB drive can be affected by a number of issues, from the performance of the host computer to interference caused by other USB devices on the same bus, to the overhead related to the drive's file system.

Ethernet Networking introduces even more complicating factors. There is the overhead of Internet Protocol addressing, as well as the file sharing protocols used, such as AFP on the Mac or SMB used by Windows, neither of which play into direct, non-networked protocols such as USB. There are also architectural issues such as the quality of the cables used and the performance of any switches (or old fashioned hubs) involved. All of these issues eat into the theoretical raw data transfer rate of Ethernet.

Fast Ethernet has a theoretical speed of 100 Mbits/sec (12 MB/sec), while Gigabit Ethernet has a theoretical speed of 1000 Mbits/sec (120 MB/sec). That suggests a double speed advantage of Gigabit Ethernet over USB (60 MB/sec), but neither protocol hits its maximum. In reality, a typical USB connected disk is roughly equal to or lesser than the throughput of a shared drive attached over a Gigabit Ethernet network.

Wireless Networking has all the complexity of traditional wired networking with the additional complications of signal strength issues such as radio interference and barriers, as well as additional overhead related to wireless transmission that commonly halves its real world throughput over the theoretical raw data rate.

- 802.11b has a theoretical speed maximum of 11 Mbits/sec with a typical transfer rate of around 4.5 Mbits/sec (0.5 MB/sec) with an ideal signal.
- 802.11g has a theoretical speed maximum of 54 Mbits/sec, with a typical transfer rate of around 23 Mbits/sec (2.5 MB/sec) with an ideal signal.
- 802.11n has a theoretical speed maximum of 300 Mbits/sec, with a typical transfer rate of around 74 Mbits/sec (9.25 MB/sec) with an ideal signal.

As the signal strength of a wireless network drops, the connection speed is automatically renegotiated and slower and slower rates until no connection is possible. The transfer rates of wireless networking make it ideal for browsing the web, as most US residents have a connection speed of around 1.5 Mbits/sec for DSL, or from 3 to 6 Mbit/sec with cable Internet service. Any version of WiFi is much faster than that.

However, very fastest wireless networking is required to perform intensive data transfers such as Time Machine backups, general file sharing, and media streaming, particularly if more than one client is using the network at once, or if one user is trying to do more than one thing with their wireless connection, such as backing up files while streaming audio to Apple TV, for example.

A Visual Speed Comparison

This chart shows the relative difference in throughput of the interfaces described above, with theoretical raw data rates in blue, and typical real world throughput in red. Note that these real world numbers are ideal peak maximums, not the average throughput users will see at all times. As detailed above, there are lots of factors that can eat into the actual real world performance. Time Capsule has performance limitations of its own, which are related to its design to primarily serve wireless clients. An upcoming segment will detail what Time Capsule itself can do.

Direct connection interfaces, such as SATA and USB, commonly deliver closer to half their theoretical maximum raw data rate, but as interfaces and drive mechanisms improve, the real world data throughput will rise. Ethernet networking interfaces, such as Fast Ethernet or Gigabit Ethernet, can hit peak transmission rates close to their maximums, but suffer from greater overhead compared to a direct connection interface.

Wireless networking throughput depends more on external factors to reach its full potential. Ideal signal strength is critically important to reach anywhere near the high end of real world throughput numbers. There are other factors that make a huge difference in wireless performance; Time Capsule and AirPort Extreme both support new features unique to the new 802.11n wireless networking protocol, including the use of multiple antennas (a technology referred to as MIMO) and the use of the 5 GHz radio spectrum. The next segment will look at the pros and cons of using this alternative frequency, which depending on the circumstances can either decrease signal range or deliver a major boost in your wireless data rate.

In addition to the cabling and protocol specifics, there are other reasons for Windows PCs to outperform Macs in USB transfers. The testing done by BareFeats in the article USB 2.0 versus FireWire compared 2004 PowerPC Macs against 3 GHz Pentium 4 PCs; since USB pushes much of its work to the CPU, the speed of the host made a big difference in how fast USB performed on the two platforms.

Their testing also revealed that the first generation of the PowerMac G5 delivered poor I/O across the board, scoring lower than even the mobile PowerBook and low cost eMac in both Firewire and USB. That indicates that the theoretical expectations for USB (or any protocol) are nearly meaningless when compared to the actual speed of the disk, processor, the implementation of the protocol itself, and other factors that might cause interference or otherwise eat up the expected maximum throughput speeds. In other words, USB does not ever run at its maximum theoretical speed rating.

Additionally, Windows file sharing and disk protocols are simpler than on the Mac, because Windows handles and presents less metadata. This lightness makes for faster disk operations at the expense of the sophistication of the Mac's higher quality file icons, richer file type and creator codes, and other features missing in Windows.

There are other factors that affect cross platform throughput as well; Mac OS X suffers some degree of overhead from new features such as Spotlight indexing, while Windows PCs are typically burdened with running anti-virus scanning software that peels away a significant edge in performance. Clearly, there are lots of factors to account for in making direct performance comparisons, and neatly presented numbers can easily hide those details in a misleading way.

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Here is another great article about network speed: