{"id":3905,"date":"2015-06-03T00:44:28","date_gmt":"2015-06-02T19:14:28","guid":{"rendered":"http:\/\/nuclearrambo.com\/wordpress\/?p=3905"},"modified":"2023-07-07T23:26:51","modified_gmt":"2023-07-07T17:56:51","slug":"beam-forming-technology-invading-consumer-applications","status":"publish","type":"post","link":"https:\/\/nuclearrambo.com\/wordpress\/beam-forming-technology-invading-consumer-applications\/","title":{"rendered":"Beam forming technology invading consumer applications"},"content":{"rendered":"
\"Figure<\/a>

Figure 1 Dell’s 802.11ac WiFi router with 8 antennas for beamforming<\/p><\/div>\n

Abstract<\/strong>: Traditional antennas used in WiFi routers were of the omnidirectional nature, meaning that they radiated in all directions equally and also received power from all directions equally. Whereas, most of the times, a user connected to WiFi router will be stationary and only a certain amount of power radiated by the router will be actually utilized. Considering this fact that most of the power is wasted, the idea of beam forming concept was born which tries to form a beam of radiation directed at the location of the user. Thus, instead of radiating power in all directions, the radio waves will now be directed only towards the user providing him with much higher signal strength and also better data rate (speed). Modern beam forming techniques have achieved the ability to form not just single beam but multiple beams in various directions. Many WiFi routers have ability to track the location of the user in the signal range<\/span> and make the radio beam follow the user wherever he is moving.<\/p>\n

<\/p>\n

Beam forming in WiFi 802.11ac standard<\/strong><\/h2>\n

Beam forming was first taken as part of the WiFi standard when the 802.11n version of WiFi was released some years ago. At that time IEEE (the institution which standardizes many electronic protocols and technologies) did not standardize how this beam forming technology has to be implemented in our WiFi routers. Anyone can implement beam forming the way he wishes. There are always more than one ways to do something. For example, Cisco might implement a different protocol in the beam forming implementation in their routers whereas Alcatel might make wireless network cards that implement the same technology in a different way. The Alcatel and Cisco products will become incompatible with each other and be of no use. Thus, 802.11n standard never had any products that utilized beam forming technology. IEEE standardized this technology in the recent 802.11ac standard and only then have products come out in the market that are able to reach multi gigabit data transfer speeds achieved due to the highly directional beam forming capabilities of consumer grade routers.<\/p>\n

Any router that has more than 1 antenna is capable of forming beams in various directions. I am sure you might have seen WiFi routers that have 2 or 3 or even 8 antennas. The purpose of these antennas is to create highly directional beams. The more the number of antennas, the higher is the ability to track user movements across the range.<\/p>\n

\"Figure<\/a>

Figure 1 Dell’s 802.11ac WiFi router with 8 antennas for beamforming<\/p><\/div>\n

How beams are formed<\/strong><\/h2>\n

Each antenna on a WiFi router is omnidirectional. That is, it radiates power in all directions. We must also keep in mind that the same antenna is also used for receiving signals from the user device. Thus, each antenna does the job of transmit and receive at same time. The following diagram will give a better understanding of the word \u201comnidirectional\u201d.<\/p>\n

\"<\/a>


Figure 2 Omnidirectional antenna radiation pattern<\/p><\/div>\n

To our importance is the \u201cAzimuth plane radiation pattern\u201d which shows that the antenna radiates equal power in the horizontal plane (X-Y axis). There exists no truly omnidirectional antenna in this world at this point in time that can radiate equal power in all directions. Which becomes clear when we see the second radiation pattern in the \u201cElevation plane\u201d, that is the vertical plane (Z-axis). Even if the antenna radiates and receives power equally in horizontal plane, it has a very different radiation characteristic in the vertical direction. Even so, we call this an omnidirectional antenna.<\/p>\n

A simplified list of steps to understand beam forming with 2 antennas<\/p>\n

    \n
  1. Now consider that there are 2 such omnidirectional antennas kept side by side in a line.<\/li>\n
  2. Distance between the two antennas is fixed and stored in the WiFi router\u2019s firmware memory.<\/li>\n
  3. Time taken for the radio wave from antenna A to B is and B to A is calculated and also stored in firmware.<\/li>\n
  4. User\u2019s location in the room is calculated dynamically by monitoring the direction from which the signals are being received from the user\u2019s device. Using this location, the angle is calculated to form the beam in direction of user.<\/li>\n
  5. Once the angle is known, the transmit signal in one of the antennas is delayed by a certain amount of time (in technical terms it is said \u201cphase shifted by certain degrees angle\u201d).<\/li>\n
  6. In the figure 2, the user is on the right hand side of the antenna array. Thus, antenna B is closer to the user than the antenna A. Wave emitted by the antenna B will reach the user first and then the wave from antenna A will reach after a certain delay.<\/li>\n
  7. If the wave from antenna B is delayed by time \u2018t\u2019, then both waves from antenna A and B will reach at the same time in the location of user. Here, time \u2018t\u2019 is the time taken by the wave to travel from antenna A to the user such that both waves from A and B reach at same time<\/li>\n<\/ol>\n
    \"Figure<\/a>

    Figure 3 Concept of Phase delay<\/p><\/div>\n

    This was a much simpler example to understand the concept of beam forming where only two antennas were involved and only one user was present. In practical situations, there could be two users sitting in different locations and beams need to be formed in both the directions. At that time, a much more complex algorithms are implemented to continuously monitor the received signal strength and track the user\u2019s location for creating a directive beam.<\/p>\n

    The beam formation is just one of the parts of the entire WiFi communication system and it has been proving itself to be very successful in providing multi gigabit wireless links to users.<\/p>\n

    Simplified protocol model<\/strong><\/h2>\n

    The WiFi router and the user device initially exchange a series of messages which help in measuring the signal quality being received by the user and the signal quality received by the router. This process is called channel calibration.<\/p>\n

    \"Figure<\/a>

    Figure 4 No steering matrix applied, no phase change<\/p><\/div>\n