[1] Natl Univ Def Technol, Res Inst 63, Nanjing 210007, Peoples R China
[2] Natl Univ Def Technol, Coll Elect Engn, Hefei 230037, Peoples R China
[3] Macau Univ Sci & Technol, Sch Comp Sci & Engn, Macau, Peoples R China
[4] Univ Kent, Sch Engn, Canterbury CT2 7NZ, England
[5] Univ Warwick, Sch Engn, Coventry CV4 7AL, England
[6] Univ Texas Dallas, Dept Elect & Comp Engn, Richardson, TX 75080 USA
[7] UCL, Dept Elect & Elect Engn, London WC1E 6BT, England