Method and apparatus for adjustable QoS based admission control and scheduling WLANs
View Patent ↗An advance over the prior art is achieved through an efficient method for an admission control algorithm and a scheduling mechanism that complement each other in providing the following three classes of service. A first class of service is termed Class 1 where users specify a nominal amount of bandwidth desired. A second, lower tier service class is termed Class 2, wherein users specify a nominal and minimum amount of bandwidth desired when entering into a network connection. A third server class is Class 3, where Class 3 users are treated as best effort users. For Class 1 users the methodology of the present invention provides a guaranteed nominal amount of bandwidth. The admission control procedure ensures that Class 1 users are admitted only if resources exist to satisfy the nominal bandwidth requirements of the Class 1 users. Class 2 users are admitted if resources exist to satisfy the minimum bandwidth requirements of the user. Class 2 users are served with a bandwidth of up to their nominal bandwidths if there is capacity left after serving the Class 1 users with their nominal capacities. Class 3 users are served only if the Class 2 users have received their nominal bandwidths.
1. A method of providing admission control in a wireless communications network, said method having at least three differing quality of service levels, Class 1, Class 2 and Class 3, wherein Class 1 of said three differing quality of service levels is guaranteed a nominal amount of bandwidth, and Class 2 users specify a minimum rate and a nominal rate, said method comprising the steps of:
admitting users to said wireless communications network such that Class 1 users are ensured to receive their nominal rates and Class 2 users receive their minimum rates; and
providing Class 2 users with their minimum rates before serving Class 3 users;
wherein one or more Class 2 users are downgraded to a lower service level to provide sufficient bandwidth for admission of a Class 1 user requesting admission,
said method of admission control attempts to achieve load balancing across potential access points in said wireless network when admitting new users, and
P th denotes a minimum power threshold requirement for user equipment to be assigned an access point, and wherein n g , n s and n b denote the number of Class 1, Class 2 and Class 3 users, respectively, at any access point (AP), wherein said method of admission control chooses an AP for a class 3 user, with received strength P that has a highest value according to the expression
(C−n s B s −n s B snom )/(n b +1)
wherein,
C =
Total available capacity at an AP,
C av =
Current available capacity,
B g =
Nominal bandwidth requirement for Class 1 users,
B s =
Minimum bandwidth requirement for Class 2 users,
B snom =
Nominal bandwidth for Class 2 users.
2. The method of claim 1 , wherein Class 2 users attempt to choose an AP with received strength P that has the maximum value C−n g B g −n s B s .
3. The method of claim 2 , wherein if there are two or more AP's that have the same maximum value, then choose the one with the least number of Class 3 users.
4. A method of providing admission control in a wireless communications network, said method having at least three differing quality of service levels, Class 1, Class 2 and Class 3, wherein Class 1 of said three differing quality of service levels is guaranteed a nominal amount of bandwidth, and Class 2 users specify a minimum rate and a nominal rate, said method comprising the steps of:
admitting users to said wireless communications network such that Class 1 users are ensured to receive their nominal rates and Class 2 users receive their minimum rates; and
providing Class 2 users with their minimum rates before serving Class 3 users;
wherein one or more Class 2 users are downgraded to a lower service level to provide sufficient bandwidth for admission of a Class 1 user requesting admission,
said method of admission control attempts to achieve load balancing across potential access points in said wireless communications network when admitting new users, and
Class 1 users attempt to select an access point (AP) having received strength P that has a largest
C/n g
where Pth denotes a minimum power threshold requirement for user equipment to be assigned an access point, C denotes total available capacity at an AP and n g denotes the number of Class 1 users at an AP.
5. The method of claim 4 , wherein admissions of Class 3 users are attempted at APs having lower Class 2 and Class 1 loads relative to other APs in said network.
6. The method of claim 5 , wherein Class 2 users are attempted to be admitted at APs with a lower number of Class 1 users relative to other APs in said network.
7. A method of providing admission control in a wireless communications network, said method having at least three differing quality of service levels, Class 1, Class 2 and Class 3, wherein Class 1 of said three differing quality of service levels is guaranteed a nominal amount of bandwidth, and Class 2 users specify a minimum rate and a nominal rate, said method comprising the steps of:
admitting users to said wireless communications network such that Class 1 users are ensured to receive their nominal rates and Class 2 users receive their minimum rates; and
providing Class 2 users with their minimum rates before serving the Class 3 users;
wherein one or more Class 2 users are downgraded to a lower service level to provide sufficient bandwidth for admission of a Class 1 user requesting admission,
said method of admission control implemented utilizing a scheduling mechanism, said scheduling mechanism includes:
a data queue and token bucket for each Class 1 user, said Class 1 token bucket flowing at a Class 1 nominal rate,
a data queue and first and second token bucket for each Class 2 user, said first token bucket flowing at a minimum rate and said second token bucket flowing at a nominal rate, and
a data queue for each Class 3 user.
8. The method of claim 7 , wherein scheduling in said scheduling mechanism comprises the steps of:
scanning token buckets for Class 1 users and minimum rate token buckets for Class 2 users;
scheduling a packet for transmission when finding a token bucket that has a token and a packet to send in the corresponding data queue;
scanning the nominal rate token buckets for Class 2 users, wherein if a user is found with both a token and a packet, the packet is transmitted and a token from the nominal rate bucket is removed; and
serving best effort queues if no Class 1 and Class 2 users are found.
9. The method of claim 8 , wherein one or more token buckets are implemented utilizing counters.
10. The method of claim 8 , wherein a minimum bandwidth is reserved for Class 3 users.
11. The method of claim 8 , wherein a token from the minimum rate token bucket is also selected for Class 2 users, if available, so as to bound Class 2 users by a nominal rate.
12. The method of claim 7 , wherein Class 2 users are provided with their nominal rates before serving the Class 3 users.
13. An admission control method for use in a wireless network, wherein users of the wireless network are each part of a particular priority class, wherein a bandwidth requirement for each user is flexible, wherein an admission request from a user arrives with a desired nominal bandwidth and a minimum bandwidth requirement and a system wide parameter is set for the maximum available bandwidth for any priority class, said method comprising:
setting nominal bandwidth of a new user to a maximum allowable bandwidth of a user class if its nominal bandwidth requirement is higher than the maximum bandwidth of its priority class
admitting a user and allocating required nominal bandwidth if the requested nominal bandwidth is less than the available bandwidth; and
if available bandwidth is less than the nominal bandwidth required, then reducing allocation to users of a lower priority class to accommodate the nominal bandwidth requirement of the new user, wherein an allocated bandwidth for users in lower priority classes is reduced according to
B after =B before −(B before −B minimum-guaranteed )/2, wherein
B after is the allocated bandwidth for users in the lower priority class after the allocation reduction, B before is the allocated bandwidth for users in the lower priority class before the allocation reduction, and B minimum-guaranteed is a minimum guaranteed rate for users of the lower priority class.
14. A method of providing admission control in a wireless communications network, said method having at least three differing quality of service levels, Class 1, Class 2 and Class 3, wherein Class 1 of said three differing quality of service levels is guaranteed a nominal amount of bandwidth, and Class 2 users specify a minimum rate and a nominal rate, said method comprising the steps of:
admitting users to said wireless communications network such that Class 1 users are ensured to receive their nominal rates and Class 2 users receive their minimum rates; and
providing Class 2 users with their minimum rates before serving the Class 3 users;
wherein one or more Class 2 users are downgraded to a lower service level to provide sufficient bandwidth for admission of a Class 1 user requesting admission,
said method of admission control attempts to achieve load balancing across potential access points in said wireless communications network when admitting new users, and P th denote a minimum power threshold requirement for user equipment to be assigned an access point, and wherein n g , n g and n b denote the number of Class 1, Class 2 and Class 3 users, respectively, at any access point (AP), wherein said method of admission control chooses an AP, with received strength P that has a highest value according to the expression
[ C −(Sum — {i =1 }^{i=n — g}B —g ( i ))−Sum — {i =( n — g +1 }}^{i=n — g+n — s}B _snom( i ))]/ ( nb +1)
C =
Total available capacity at an AP,
C av =
Current available capacity,
B g =
Nominal bandwidth requirement for Class 1 users,
B s =
Minimum bandwidth requirement for Class 2 users,
B snom =
Nominal bandwidth for Class 2 users.
15. The method of claim 14 , wherein Class 2 users attempt to choose an AP with received strength P that has the maximum value
[ C −(Sum — {i =1 }^{i=n — g}B —g ( i ))−Sum — {i =( n — g +1 }}^{i=n — g+n — s}B — s ( i ))].