Rate selection for channel selection in flexible WDM networks

1. A method implemented in a communications system and comprising the steps of:

obtaining, by a processor, a first data rate in a flexible wavelength division multiplexing FWDM network; and

applying, by the processor, a recursive rate selection for determining a given data rate from the obtained first data rate such that a required spectrum over said network for said given data rate is minimized, said first data rate being lower than said given data rate;

wherein said recursive rate selection comprises recursively determining a spectrum and a set of channels required for data rate n using said spectrum and set of channels required for a data rate n′, where n′<n, wherein if an optimal said spectrum and set of channels are known for each data rate n′<n, then said optimal spectrum for said data rate n being obtainable as follows:

X n =0 if n≦ 0

X n =min lEL [x l +X n-1 ] if n> 0,

where l denotes a channel line rate, n′=n−l, X n being a total required spectrum for data rate n, x l being a required spectrum for a channel operating at a line rate lεL.

2. A method implemented in a communications system and comprising the steps of:

obtaining, by a processor, a first data rate in a flexible wavelength division multiplexing FWDM network; and

applying, by the processor, a recursive rate selection for determining a given data rate from the obtained first data rate such that a required spectrum over said network for said given data rate is minimized, said first data rate being lower than said given data rate;

wherein said recursive rate selection comprises, for each line rate l, offered by heterogeneous channels in said FWDM network where lεL with L being a set of line rates of channels in said FWDM network,

finding λ l =x l+X n-l ,

firstly recording a respective line ratio l into μ l and recording a previous data rate n−l into β l , with λ l being a total spectrum of a set of channels which consists of at least one channel with line rate l which can be determined by using an existing solution of the data rate n−l,

secondly recording of said line rate into μ l whose spectrum is taken into account in determining λ l , and

thirdly recording a previous said data rate n−l into β l .

3. The method of claim 2 , wherein said recursive rate selection comprises selecting line rate l for which λ l is a minimum and recording a respective said line rate μ l into q n and recording a previous said data rate β l into p n , resulting in a minimum said spectrum.

4. The method of claim 3 , wherein said recursive rate selection comprises, if said data rate n is still less than a data rate of a connection, γ, incrementing said data rate n and repeating said firstly, secondly and thirdly recording steps.

5. The method of claim 3 , wherein said recursive rate selection comprises:

initializing data rate n to a requested said data rate of a connection, γ;

including said line rate, q n , into an optimum set of channels Y γ ; and

checking whether said data rate n is less than or equal to 0, and if data rate n is positive then said data rate is reinitialized to p n which is said previous data rate; and

returning said optimal set of channels Y γ and an optimal said spectrum, X γ .