Two-tier call admission control method in IEEE 802.11 WLAN

• US 7,792,028 B2
• Filed: 11/30/2006
• Issued: 09/07/2010
• Est. Priority Date: 09/22/2006
• Status: Expired due to Fees

• Current Assignee: National Chiao Tung University (Government of The Republic of China)
• Original Assignee: National Chiao Tung University (Government of The Republic of China)
• Inventors: Shih, Yuan Hwai, Huang, Ching Yao
• Primary Examiner(s): Juntima; Nittaya
• Application Number:
  US11/606,419
• Publication Number:
  US 20080075050A1
• Time in Patent Office: 1,377 Days
• Field of Search: 370/230, 370/252, 370/338, 370/401, 370/412, 370/465
• US Class Current: 370/230
• CPC Class Codes: H04W 28/16 Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

The present invention discloses a two-tier call admission control algorithm in IEEE 802.11 WLAN. The two-tier call admission control algorithm is given to improve the overall system throughput and guarantee the quality of service of every single user in the WLAN.

Claims

1. A two-tier call admission control method in an IEEE 802.11 WLAN, used to admit of provision of high quality of service, comprising the following steps:

having a single user and an overall system correspond respectively to a first layer testing and a second layer testing;

controlling a measurement of a physical layer and a testing of the physical layer to serve as the first layer testing;

allowing a plurality of station platforms that only pass the first layer testing to initiate an associated request to the overall system, and then get into the second layer testing; and

introducing a buffer time into the second layer testing in order to compensate for a TXOPs (Transmission Opportunity) variation of the station platforms induced by status change of the physical layer wherein the method further comprising a parameter G, which denotes the sum of each of the TXOPS and is defined by;

$G=\underset{i=1}{\overset{k}{\sum <br><br>}}<br><br><br><br>T\times <br><br>{\mathrm{OP}}_i,$

where k and i are integers;

and a parameter SI (service interval) which is defined by SI=min (DB_i), ∀

i, where DB denotes a delay bound of a communication throughput, and i is an integer.

2. The two-tier call admission control method in accordance with claim 1, wherein a transmission probability between different modes, which is served as a parameter in calculation of a buffer timer the buffer time, is defined by a three-dimensional Adaptive Auto Rate Fallback (AARF) Markov chain described by the following equations:

$P_{{\mathrm{down}}_m}=P<br><br>\left(m-1❘<br><br>m\right)=\frac{P<br><br>\left(m-1\bigcap <br><br>m\right)}{P<br><br>\left(m\right)}=\frac{\underset{d=1}{\overset{4}{\sum <br><br>}}<br><br><br><br>\left\{\begin{array}{c}{P}_f^2<br><br>\left(m,\mathrm{SNR}\right)\times <br><br>\left[\underset{k=1}{\overset{T_d-1}{\sum <br><br>}}<br><br><br><br>b<br><br>\left(m,k,d\right)+b<br><br>\left(m,D,d\right)\right]+\\ P_f<br><br>\left(m,\mathrm{SNR}\right)\times <br><br>\left[b<br><br>\left(m,p,d\right)+b<br><br>\left(m,0,d\right)\right]\end{array}\right\}}{\underset{d=1}{\overset{4}{\sum <br><br>}}<br><br><br><br>\left\{\underset{k=0}{\overset{T_d}{\sum <br><br>}}<br><br><br><br>b<br><br>\left(m,k,d\right)+b<br><br>\left(m,P,d\right)+b<br><br>\left(m,D,d\right)\right\}}$ $P_{{\mathrm{up}}_m}=P<br><br>\left(m+1❘<br><br>m\right)=\frac{P<br><br>\left(m+1\bigcap <br><br>m\right)}{P<br><br>\left(m\right)}=\frac{\underset{d=1}{\overset{4}{\sum <br><br>}}<br><br><br><br>\left\{\begin{array}{c}{P}_s^{10}<br><br>\left(m,\mathrm{SNR}\right)\times <br><br>b<br><br>\left(m,P,d\right)+P_s^{T_d}<br><br>\left(m,\mathrm{SNR}\right)\times <br><br>[b<br><br>\left(m,D,d\right)\\ +b<br><br>\left(m,0,d\right)]+\underset{k=1}{\overset{T_d-1}{\sum <br><br>}}<br><br><br><br>\left(P_s^{T_d-k}<br><br>\left(m,\mathrm{SNR}\right)\times <br><br>b<br><br>\left(m,k,d\right)\right)\end{array}\right\}}{\underset{d=1}{\overset{4}{\sum <br><br>}}<br><br><br><br>\left\{\underset{k=0}{\overset{T_d-1}{\sum <br><br>}}<br><br><br><br>b<br><br>\left(m,k,d\right)+b<br><br>\left(m,P,d\right)+b<br><br>\left(m,D,d\right)\right\}}<br><br>$

where m denotes a present mode of the station platform, b is a state probability, P_s represents a probability of a successful transmission of a packet, P_f represents a probability of a failed transmission of a packet, d denotes a relative three-dimension value, P_down represents a probability of transmission decrease, P_up represents a probability of transmission increase, P denotes that the station platform has completed 10 consecutive transmissions and is just going to transmit a plurality of parameters of a probing packet, SNR represents a signal-to-noise ratio of the station platform from sudden change, D denotes a plurality of parameters concerned with a transmission rate, and T_d and k are related threshold values.

3. The two-tier call admission control method in accordance with claim 1, further comprising a parameter BT (buffer time), which is defined by the following equation:

$\mathrm{BT}=\underset{l=1}{\overset{k}{\sum <br><br>}}<br><br><br><br>N_i\times <br><br>L_i\times <br><br>\left(P_{{\mathrm{down}}_{i,m}}\times <br><br>{\mathrm{\delta <br><br>}}_{{\mathrm{down}}_{i,m}}-P_{{\mathrm{up}}_{i,m}}\times <br><br>{\mathrm{\delta <br><br>}}_{{\mathrm{up}}_{i,m}}\right)+\mathrm{\Delta <br><br>}$

where δ

_down denotes one bit'"'"'s time difference when a mode is decreasing, δ

_up denotes one bit'"'"'s time difference when a mode is increasing, and Δ

denotes uncertain characteristics in compensating each communication throughput, k and i are integers, N, L are two communication parameters, P_down represents a probability of transmission decrease, P_up represents a probability of transmission increase and m denotes a present mode of the station platform.

4. The two-tier call admission control method in accordance with claim 1, further comprising a parameter deadline, which is defined via the following equation:

Deadline=SI−

BT,

where SI represents the service interval and BT represents the buffer time.

5. The two-tier call admission control method in accordance with claim 1, further comprising a decision criterion, which is defined via the following equation:

(G>

Deadline)∩

(RD>

N_reject),

where RD denotes a rejection density, N_reject denotes a prescribed value, G represents the overall sum of time of all the platform stations in the SI period and Deadline denotes a bound that is set to detect whether the system is still having a capability to compensate for each transmission opportunity (TXOP) extension, if the equation holds, then the overall system rejects any new request for connection, if the equation does not hold, then the overall system consents to new associated requests.