# A Novel Power-Saving Transmission Scheme for Multiple-Component-Carrier Cellular Systems
## 3 Problem Description  
### System Model  
For the purposes of the present study, we focused on the downlink data transmissions in an OFDMA-based multi-CC BS system of a single cell. In this scenario, the cell itself is comprised of \(n\) user terminals, with each user terminal being indexed as user-\(k\). In this model, the smallest allocation unit for resource scheduling is a sub-channel spanning 12 sub-carriers for which the bandwidth is denoted as \(b_{\text{sub}}\). In addition, it is assumed that only a single user can be assigned to a given sub-channel. Moreover, the amount of time, in seconds, spanning a specific number of consecutive OFDMA downlink frames is defined as the smallest transmission unit and denoted as \(\alpha\). The notation \(s\) is used to denote the current scheduling round. In this context, \(\alpha\) is set equal to 1 in order to avoid re-defining the unit of \"power\" and in order to allow reasonable required computation time for the scheme employed. It is further assumed that there are a total of \(c\) CCs located in different frequency bands. These CCs, which are indexed by \(i\), can be utilized for transmission. Without loss of generality, for a user with a given specific transmission power, the data rates supported by the CCs in the higher frequency bands are lower than those supported by the CCs in the lower frequency bands. In this study, the CC with \(i=1\) was regarded as the primary CC (PCC), while the others were regarded as the supplementary CCs (SCCs). For data transmissions, the PCC was always used as the main CC and was thus set to always be activated, while the SCCs were only used when the traffic was relatively heavy in order to supplement the PCC. As a result, there are naturally \(c\) kinds of combinations for these SCCs and the PCC. More specifically, if \(\Omega\) is defined as the set of all the combinations of CC configurations involving at least the PCC, then the configuration status vector in round \(s\) can be defined as \(v^{(z)}(s)=[v_{1}^{(z)}(s),v_{2}^{(z)}(s),...,v_{c}^{(z)}(s)]\), where \(z\) denotes the index for the configuration being utilized in \(\Omega\), and \(z=1\), \(2\),..., \(|\Omega|\). Note, then, that \(|\Omega|=c\). We can set \(z=x\) to indicate that the CCs with \(i=1\) to \(x\) are activated and that no other configurations are permitted. As such, for a specific configuration \(z\) in round \(s\), \(v_{i}^{(z)}(s)=1\) if CC-\(i\) is activated; otherwise, it equals 0. Furthermore, we also assume that CC-\(i\) consists of \(\ell_{i}\) sub-channels. Figure 1 presents a conceptual construction of the system model from a systemic point of view, where it is comprised of a classifier, an RT processing queue, an NRT processing queue, an admission gate, a scheduling queue, a scheduler, and \(c\) OFDMA-based CCs. The data of the various users are transmitted at the session level. In the classifier, all the user session requests are categorized as either RT or NRT sessions, and from the classifier, they are then forwarded in sequence to, respectively, either the RT processing queue or the NRT processing queue. If allowed, these session requests then pass, at the start of each scheduling round, through the admission gate, after which they are buffered to the scheduling queue where they then wait for the scheduler to accept or deny their requests for transmissions. For convenience, in some parts of this paper, the NRT users and the RT users are indexed as type-\(m\) users, with \(m=1\), \(2\), respectively. In addition, the term \(\Re^{(m)}(s)\) is used to denote the set of type-\(m\) users in the cell for round \(s\); \(\Re_{w}(s)\) is used to denote the set of active users with session requests awaiting the scheduler decision in the scheduling queue for round \(s\); and \(\Re_{s}(s)\) is used to denote the set of active users whose sessions are actually being served during round \(s\).