problem with pagination

i use pagination in codeigniter . and show page number but dosn't show previous and next button


controller code

PHP Code:

$config['base_url']    = base_url() . 'track/category/' . $title . '/page/';
                    $config['total_rows']  = $this->custom_model->GetcountDataByCategory('track', $id);
                    $config['per_page']       = 30;
                    $config['uri_segment'] = $this->uri->segment(5);
                    $page                  = ($this->uri->segment(5)) ? $this->uri->segment(5) : 0;                    
                    $this->pagination->initialize($config);
                    $data['pagination']    = $this->pagination->create_links();                    
                    $tracks                = $this->track_model->getDataByPaging($id, $config['per_page'], $page); 


model code : 

PHP Code:

public function getDataByPaging($id, $limit, $start){
        $publishDate = strtotime(date('d F Y h:i A'));
        $this->db->select('t.id  tid,t.artist_id  tartistid,t.remixer tremixer,t.genre_id  tgenrei,t.category_id tcategory,t.title  ttitle,t.cover  tcover,t.energy,t.label,t.on_sale tonsale,t.featured,t.description,t.publish_date,t.release_date,t.count_download,t.key,t.bpm,t.url,t.lik,artists.id,artists.artist_name,g.id gid,g.name,cat.id catId,cat.title catTitle,');
        $this->db->from('track AS t');
        $this->db->join('artists','artists.id = t.artist_id');
        $this->db->join('genres AS g','g.id = t.genre_id');
        $this->db->join('category AS cat',"cat.id = t.category_id");
        $where = "t.publish_date = 'NULL' OR t.publish_date <= $publishDate AND t.category_id = $id";
        $this->db->where($where);
        $this->db->order_by('t.release_date','desc');
        $this->db->limit($limit, $start);
        $query = $this->db->get();
        return $query->result();
} 


here